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Showing posts with label Forensic science. Show all posts
Showing posts with label Forensic science. Show all posts

Monday, January 13, 2014

Digital Footprints - Computer Forensics and Digital Evidence: Information for Writers

_____________________________

This office is Grand Central.” He plugged a new flash drive into the computer.
      “Are you finding what you need?” I asked.
      “Some of it. They have security on top of security.”

     ~ Missing Lynx





If you're writing a contemporary suspense/thriller/crime novel, then digital information is an important angle to consider.

Modern technology makes certain crimes easier to carry out than ever before, indeed there are certain crimes that exist now that were not possible before computers became generalized to the world population.

How many of you have been at the end of an African lottery win phishing expedition? Conversely, if the criminal is not aware of how digital forensics can help an investigation, it can also make crime harder to get away with.



Map showing the Strategic Alliance Cyber Crime...
Map showing the Strategic Alliance Cyber Crime Working Group member countries and lead agencies (Photo credit: Wikipedia)


Most interrogators working with computerized information are called Digital Forensic Investigators. Apparently calling them computer-geek-cops is frowned upon.



Deutsch: Micro USB Ladekabel für Mobiltelefone
 (Photo credit: Wikipedia)

They cover such crimes as:

* Cyber bullying
* Child porn and child
   exploitation
* Pirating - software, music,
   videos, and
  other copyrighted work
   like books.
  Link to novalist John
  Dolan's blog post
  about his experience with
  pirating. Just FYI
* Credit card fraud
* Altering medical data for insurance fraud
* Espionage
* Terrorism
* Corporate crimes
* Pharming - Pretending to be a legitimate
   organization when they are not
* Phishing - Trying to defraud people


Video Quick Study (3:43) Phishing and Pharming examples
Video Quick Link (3:28) - excellent overview of digital crimes
Video Quick Study (6:44) - This is Josh Moulin who taught at
                                WPA 2011. He is explaining what he does,
                              listen carefully to his mode of speech and his
                              vocabulary. This is not specialized speak
                              for the interview. This is how he spoke with us.
                              (Don't go to the website he offers; it is
                              incorrect).
                             * Includes tips for how to protect a child on line
                             * Tips on general computer safety



The first hurtle to jump is just identifying that there is an issue.

* Is this a glitch in a program? A human error? Or, is this a crime?
   Often times computer crimes are hard to discover.
* Did the person have widely scoped criminal intent such as a
   terrorist? Or was this a bored teenager hacking into a system to
   see if he could?


Then they start looking for a suspect.

Digital Forensics Experts will:
1 Trace Back - the computer experts try to find the source
   computer - computer from which the attack originated - by
   following the trail of addresses (IP Addresses)
2. Scrutinize the computer system of the entity that was
   compromised called the target.


Once the investigators have narrowed in on the suspect, they need to prove:

MOTIVE
* Did the person have motive for perpetrating a crime and what
   was it? Motivators might include:
   ` Curiosity - like hackers to see if they can.
   ` Money
   ` Victimization (such as stalking or pedophilia)
   ` Power/leverage/ revenge

KNOWLEDGE and MEANS
* Believe me, I could have all of the motivation in the world, BUT
   if my scheme includes anything more than
   using a word processor, you've got the wrong girl.

ACCESS to perpetrate such things as:
* Data mining for materials that would benefit a criminal such as
  credit card numbers.
* Logic Bombs - "is a piece of code intentionally inserted into a
   software system that will set off a malicious
  function when specified conditions are met. For example, a
  programmer may hide a piece of code that
  starts deleting files, should they ever be terminated from the
  company." More information here.
* Opportunity to perform alterations of computer logs to show that
   the activity happened at a different time
    or date. (Investigators must look at the time/date stamp and make
   sure these were not tampered with,
    for example)



English: DCIS special agents investigate cyber...
English: DCIS special agents investigate cyber crime within DoD. (Photo credit: Wikipedia)


In order to develop the motive, access, and means, the investigators will collect evidence. Evidence is collected, analyzed, and stored.


Traditional Investigation
1. Interview eye witnesses - did anyone see or hear anything
    pertaining to the crime?
2. Conduct surveillance
    * Electronic surveillance might include pretending to be a target
       such as posing as a thirteen-year-old girl.
    * Discovering if the suspect would have been some how
       UNABLE to perform a cyber crime by location,
       activity, etc. Ex. a scuba diver would probably have an alibi if
       they were underwater.
    * Smart phones with internet capability make this difficult at
       times; though again, everything leaves a digital
       trail, so it might just be helping investigators.

Digital investigation

In order to access digital information from the target computer system, the investigators would need owner permission. If they wish to gather the information from the source computer they will need a warrant. 
* The investigators might want to do this surreptitiously so as not
    to let the suspect know that they are
    being investigated.
* They may confiscate the equipment.


COLLECT: 4 strategies for collecting the digital footprint.


English: A portable Tableau forensic write-blo...
English: A portable Tableau forensic write-blocker attached to a hard disk drive (Photo credit: Wikipedia)

1. Seizure - bag, tag, and send devices to
    the forensics laboratory.
   * Ever growing number of devices with
      huge amounts of memory makes long
      back logs.
   * No way to differentiate between items
      that might contain evidence and items that
      have no relevance.
2. Onsite Imaging
    * Time consuming
    * Issues of contamination
3. Digital Triage with Boot CD or Thumb
    Devices
    * Cannot cope with cell phones, GPSs or
       similar devices
    * Can contaminate the data that is being
       harvested.
4. Onsite collection with specialized equipment such as Spektor
    * The one in this video was developed for investigators who do not specialize in digital forensics. So your
      Joe-cop could collect the evidence with maximum forensic control.
   * Can handle cell phones and GPS devices.
   Video Quick Study  (4:53) Promotes Spektor - but is a good quicky-overview of the collection techniques


English: A Tableu internal forensic write-prot...
English: A Tableu internal forensic write-protection module (Photo credit: Wikipedia)


Once the device is in the hands of the investigator:

1. They make back up copy (working copy)
    * Original data must stay intact allows it to be presented later in original condition if needed in court.
    *  Making the copy is called imaging.
    * Working Copy Master (the original copy) is used to make
       more copies. The original WCM is archived along with the 
       original data.
    * Investigators work on one of the other versions - if it is
       somehow corrupted then the investigators can
        make a fresh copy from the WCM

Plot point: How are the investigators sure that the copy is correct? They use a hash value - program that converts data into whole numbers that are added up. These sums are compared and if they match, then investigators know that they have an exact replication. This is a very cool little piece to manipulate in a plot line so I'm including this LINK to an academic paper concerning its use.


2. Examination computer - the data is
Image found on Facebook
    removed by
   a. USB
   b. SCSI  small computer interface
   c. Computer firewires link to howstuffworks article
 
  The machine is placed inside of a
   protective box that prevents
   someone at a remote location
   from communicating with the data
   and, for example, wiping the hard
   drive.

Analyze - specifically and carefully

Preserve - with a documented chain of custody to maintain the integrity of the evidence for presentation in court.


DATA STORAGE - 

Where do people (the good guys and the bad guys) look for data?

Slack space - where data goes when your heroine thinks she deleted it.
Any digital data storage device can be used to...
 (Photo credit: Wikipedia)
* Unencripted passwords and bank account
   numbers could be found here by
   investigators
* Hackers can go and harvest that same kind
   of data
Browser history (opening individual files)
Keyword search 
Metadata searches ex:
*who created it
* when
* where was it received and by whom

Video Quick Study (5:07) Great easy-to-understand description of why data doesn't disappear when your heroine deletes her files.


Another way Digital Forensics Investigators gather evidence is cell phones via GPS.
Cell phones will ping off of a cell tower and give a general location. This can help establish an alibi; it can
also place a criminal in the vicinity of the crime. Investigators have to be careful in areas that have many cell towers because there can be bleed over. This happens when someone is near the overlapping area of two towers. PLOT TWIST if there is bleed over, it could put your heroine near the scene of the crime instead of in bed reading a good book like Virginia Is for Mysteries. (yup, I just unabashedly plugged my anthology!) Your heroine's lawyer might just use bring in an expert to testify on this very subject. Where was she the night of the murder? - Can't tell from her cell phone pings.

But this is all very cops and robbers. Your plot line runs more along the line of a savvy heroine who isn't taken advantage of. By anyone. What can she do? Your heroine doesn't have to be a forensic security geek - she can get simple tools like Recover It. LINK (quicky advertising video that shows this in action)


Pertinent Laws:

Cable Communications Policy Act 1984 link
Electronic Communications Privacy Act 1986 link
Digital Milennium Copyright Act 1998 link
USA Patriot Act 2001 (Uniting and Strengthening America Providing Appropriate Tools Required to Intercept and Obstruct Terrorism) link



See how this article influenced my plot lines in my novella MINE and my novel CHAOS IS COME AGAIN.


Thank you so much for stopping by. And thank you for your support. When you buy my books, you make it possible for me to continue to bring you helpful articles and keep ThrillWriting free and accessible to all.



Friday, December 6, 2013

Skeletons in Her closet: The Forensics of Skeletons for Writers



___________________________________________________________________________________

I curled up like a cat on Miriam’s living room couch with a cup of hibiscus tea steeping on the table beside me. Miriam was on the phone with the police, jotting notes about a case they wanted her to work for them. Someone’s Great Dane came home this morning with a human skull in his mouth. The detective needed a jump-start – some information to get going with while the skull waited its turn on the forensics lab shelf. ~ WEAKEST LYNX










Writers, if your crime scene includes skeletal remains or even remains that have advanced to a soupy mess, the person who is called in to take control of the bones is a FORENSIC ANTHROPOLOGIST.
***NOTE: The forensic anthropologist is applying their post graduate studies in biology and anatomy as well as their understanding of trauma to research the bones. They do not solve the crime. They do not interview suspects or witnesses (LINK to Interrogation for Writers). They simply: study, document, report, testify (where necessary).


Forensic anthropologists can help identify ske...
Forensic anthropologists can help identify skeletonized human remains, such as these found lying in scrub in Western Australia, circa 1900–1910. (Photo credit: Wikipedia)



Forensic Anthropology - Dem Bones!
Video Quick Study (3:13) Tanya Peckmann talks about her job.

Servicemembers search for POW/MIAs on Wake Isl...
Servicemembers search for POW/MIAs on Wake Island Greg Berg uses a sifter to look for bone and artifacts at a dig site Jan. 12 on Wake Island. Mr. Berg, a forensic anthropologist, was sent to do a site survey after Wake Island officials notified the Joint POW/MIA Accounting Command of bones located on the island. JPAC officials are charged with achieving the fullest possible accounting of all Americans missing as a result of past conflicts. (U.S. Air Force photo/Tech. Sgt. Shane A. Cuomo) (Photo credit: Wikipedia)
The job of Forensic Anthropologists is to make some determinations concerning the skeleton that was discovered or exhumed. They are called in by officials to remove the remains.
* Remains are placed in a body bag for transport to a
   forensic laboratory.
* The remains are reconfigured to a supine position, and
   photographed.
* Any remaining soft tissue is cut away from the skeleton
* The bones are abraded with steel wool to remove dirt,
   bugs, and soft tissues.
* The bones are then soaked in a chemical solution to
    further clean and prepare them for examination.

This Video Quick Study (12:04) is a non-narrated look at a forensic anthropologist team at work





The Forensic Anthropologists attempt to make the first sets of identifying data:
* Approximate age
FAFG - coded corpse
FAFG - coded corpse (Photo credit: xeni)
* Sex
* Size/height
* Ancestry


AGE:


* Teeth and bone growth help to identify the proper age.
* Precise age determination is easier in children than in adults because of the statistical probability of various
   developments taking place in teeth and bone fusion/growth plates.
* Age results for adult remains are given in broad ranges.
* 206 is the average number of bones of an adult.
* An adult  skull has approximately 22 bones.
Parts of a long bone
Parts of a long bone (Photo credit: Wikipedia)
* A newborn skull has approximately 44 bones.
* In assessing age in children, the long bones of the body
   show dramatic changes with age.
*ossification of the growth plates follow general
  standards:
  - First growth plates close at the elbow
  - next ankles, knees, hips, then shoulders.
  -  The last growth plate to close up is the central tip of
     the clavicle around 23-28. (health and nutrition
     effects this age span)

Video Quick Study (1:48) - bone changes from infancy to adult

   * Teeth form from crown to root.
   * At birth primary teeth are already present in the jaw.
   * At 6 mos most infants have visible teeth.

Video Quick Study (3:17) Dr. Snow identifies Gacy's
                                        victims by age.


English: diagram of a human female skeleton, b...
. (Photo credit: Wikipedia)

SEX:

* Prior to puberty, the skeletal remains cannot
   be identified as male or female without DNA.
* A pelvis in a female is wider from front to back.
* Joints tend to be larger on males.

THE SKULL - this information is statistically correct. Measurements are made and compared at different points on the skull to determine a statistical probability rather than a 100% certainty.
* Male occipital protuberance is larger to attach larger
   neck muscles.
* Male brow ridges are larger
* Women tend to have higher smoother foreheads.
* Male jaws tend to be at a 90 degree angle with
   squared corners.
* Women's jaws tend to be smoother with
   pointier chins

Video Quick Study (2:35)





the adult skull is normally made up of 22 bone...
the adult skull is normally made up of 22 bones. Except for the mandible, all of the bones of the skull are joined together by sutures, semi-rigid articulations formed by bony ossification, the presence of Sharpey's fibres permitting a little flexibility (Photo credit: Wikipedia)

SIZE AND HEIGHT


* Is best identified from a full skeleton.
* Statistics have been developed to allow a range based on skull size.

the adult skull is normally made up of 22 bone...
the adult skull is normally made up of 22 bones. Except for the mandible, all of the bones of the skull are joined together by sutures, semi-rigid articulations formed by bony ossification, the presence of Sharpey's fibres permitting a little flexibility (Photo credit: Wikipedia)

ANCESTRY

* Without DNA ancestry is difficult.
   LINK to DNA article
* DNA is best harvested from the teeth, though it is
   possible to extract from bone.
* Skull structure yields the biggest clues about
   race/ancestry based on math formulas.
* Few people today come from a racially pure
   ancestral line, making identification more difficult.
* In order to apply the statistics to ancestral
   identification, a fairly intact skull is required.


Skeletons under excavation at Walkington Wold
Skeletons under excavation at Walkington Wold (Photo credit: Wikipedia)

Beyond excavation (LINK to Crime Scene Info for Writers), and the preliminaries of age, sex, size and ancestry, a forensic anthropologist can offer investigators other identifying information:
* History of bone breakage
* History of surgical interventions such as ACL replacements and other injuries where screws and implants
   were used.
* Nutrition over the life span
* Toxicity over time such as arsenic or mercury.
* Exposure to heavy metals like lead

* They can also help determine the number of skeletons in a mass destruction such as a large fire or plane
   accident.

They can inform and testify about stab wounds and what type of weapon might have been used through trauma analysis.
* Was the break:
   - antemortim trauma - before death like healed fracture or screws from surgical repair.
   - post mortem trauma - what happened to skeleton after the death - like an animal
   - perimortem trauma - bone damage at or around the time of death, such as  a broken jaw or cracked
     skull.

To gather this information they use CAT scans, and other medical diagnostic machinery.
Video Quick Study (3:51) Discusses high-tech tools.





Thank you so much for stopping by. And thank you for your support. When you buy my books, you make it possible for me to continue to bring you helpful articles and keep ThrillWriting free and accessible to all.

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Monday, October 7, 2013

Crime Scene 101 for Writers: Decisions. Decisions.

___________________________________________

CRIME SCENE DO NOT CROSS / @CSI?cafe
 (Photo credit: Wikipedia)
I just finished reading Mike Roche's book, THE BLUE MONSTER. It was a wonderful window into urban police investigation. One of the things that I appreciated about the book was understanding how individual competencies in processing a crime scene can make all of the difference in bringing a perpetrator to justice.

To this end, I thought that this week on the blog we could look at some decisions that writers can make and different points at which things can go well, or a writer could twist the plot.


WRITERS' DECISION MAKING


STEP ONE -  Is it safe to go on the scene?

1. Do you have a hazardous environment called a HOT ZONE?
   A  Hot zones can be created by
       * natural disaster - such as Tsunamis in Japan, floods, fires, and storms
       * mass disasters - such as terrorism
       * crimes - like the anthrax filled envelopes through U.S. Postal Service
       * accidents
   B. Hot zones might include
      * nerve gas
      * radioactive materials
      * nuclear threat
      * chemicals creating toxic and/or combustible threats
      * bio-hazards such as pathogens, venom, and parasites along
         with other disease causing organisms

2. Is the bad guy still on the scene?

3. Did they plant booby-traps or bombs Link to bombs article


STEP TWO - Will the first response team get there in time?
* To save the victim(s)?
* To save the house?
* And in their attempts to preserve life and/or preserve property
   will they damage the evidence to
   make it harder to solve the crime?


STEP THREE - How effective will your First Responders be when they contain and secure the scene?


Soldiers of the United States Army Criminal In...
. (Photo credit: Wikipedia)

* Only someone with a good reason to be at the crime
   scene is allowed in the area - this precludes the media,
   the family, and PI's. In Janet Evanovich's books
   Stephanie Plum really can't just walk in and look
   around because she happens to be doing Morelli.
* Others who might contaminate your scene and
    twist your plot might include looters and bystanders
* An officer has to stand at the entrance of the scene
   and log in everyone who enters and exits the police
   tape including the precise times when they entered and
   exited.
* Others who enter a crime scene can introduce
   Finger prints Link to finger print article
   Foot prints Link to footwear article
   Hair
   DNA Link to DNA 101 article
   Tire prints

Now this might be a good place to talk about Locard's Exchange Principle:

Whenever someone moves throughout an environment there will be an exchange of materials.
* A person will pick up materials such as animal hair, dirt, and fibers and take them away with them.
* A person will leave trace evidence showing that they were there - fingerprints, hair strands, DNA from spit
   or blood.
* The longer that two people are in contact and the more intense their exchange the more trace evidence will
    be left in place.

Imposing Lokard's Theories there will be a transference. This is why any superfluous people need to be kept from the scene.
* When extra information is introduced it slows the process and creates extra work for the investigators
   because they have to sort through all of the data.

Another reason to keep others at a distance:
* Public access has to be restricted so that someone with a cellphone etc. won't be releasing information
   to the public.
* The police typically only release information that is critical to identifying the perpetrator.
* They keep the rest quiet so they can monitor the story.
   For example, in interrogation Link to Interrogation article a suspect lets slip a piece of information that
   only the perpetrator or someone who had seen the scene would know. This is a big piece of evidence
* This also helps prevent copy cat cases because the full MO has not been revealed. Maybe that's just what
   your plot needs.






A Crime Scene at the National Museum of Crime ...
A Crime Scene at the National Museum of Crime & Punishment (Photo credit: Wikipedia)


STEP FOUR : How competent are your investigators in gathering and processing evidence?


VIDEO QUICK STUDY (11:41) good overview poor sound quality.
VIDEO QUICK STUDY (25:52) A little long but this is the process from the military (US Army)

* Proper warrants are obtained (a property owner can give consent for searches)
* A search strategy is developed by the officer in charge
   This prevents the crime techs from damaging or overlooking evidence
   This usually happens before the investigators enter a scene. Everything must be considered even the spatial
   relationships of objects, blood spatter patterns etc.
* There are four main types of searches -
English: Footwear impressions left at a crime ...
English: Footwear impressions left at a crime scene. (Photo credit: Wikipedia)
   line search 
   circular (or spiral) search 
   serpentine search 
   funnel search
* Evidence is identified -
   1 Trace Evidence - (also called Micro-evidence)
      tiny pieces like sand, saliva, latent prints.
   2 Real Evidence  (also called Tangible Evidence
     and Macro Evidence)-  physical objects
      that inform a case or played a part in the incident.
 * Everything in the area is potential evidence
 * Assumptions are made prior to scientific analysis -
    Is it blood? Is it cocaine?
 * Field Tests are conducted (like blood swabs)
 * Pattern Evidence - Helps to understand the scene.
     This is protected with photography (digital and
      video) VIDEO QUICK STUDY (5:39)
   * Maps are created
   * Measurements of all pertinent pieces of evidence
      are documented.
   * All objects are measured from one set
      point called a datum. 
   *This is sometimes done with
     portable computerized mapping systems called
     Total Station Serving Systems
   
VIDEO QUICK STUDY  (9:51) excellent lecture on evidence collection. Shows process and equipment in use.
*Macro search
   1. hunt and peck
   2. flashlight
   3. alternate light Link to alternative light article go to
                         second half
   4. taping
* Micro Search
    1. vacuum
    2. fingerprinting
    3. using chemical solutions (such as BlueStar or Luminol)
    4. swabs


STEP FIVE - Did your responders process everything correctly so that it is useful in making a case and also permissible in court?


* Documentation
   `Crime Scene inventory list is created identifying each marker
   ` Chain of custody list
* Preservation
* Transportation of evidence

STEP SIX - The investigators hand the evidence over to the scientists and a whole new set of complications can twist your plot. Have fun!

See how this article influenced my plot lines in my novella MINE and my novel CHAOS IS COME AGAIN.




Thank you so much for stopping by. And thank you for your support. When you buy my books, you make it possible for me to continue to bring you helpful articles and keep ThrillWriting free and accessible to all.

Monday, September 30, 2013

Walking Through Forensic DNA Basics: Information for Writers

______________________________________________________


Animation of the structure of a section of DNA...
 (Photo credit: Wikipedia)
This week I had the opportunity to go down to Richmond to visit the FBI headquarters. A handful of Sisters in Crime Members were being hosted by the FBI Evidence Response Team. I want to thank the team for sharing their expertise. (Names and images are withheld for security purposes)

That night I learned a lot about processing the scene of a crime, collecting everything from foot prints BLOG LINK - Footwear Evidence to  fingerprints BLOG LINK to Fingerprint Evidence to fibers.

But the gold star belongs to DNA. DNA has risen to be THE  best available evidence because the laboratory results are statistically linked to a single person and exclude all others.

Did you know that with the improvements in science, they can now trap enough DNA in a fingerprint to create DNA profile?

If you are writing a story that involves a crime, it's likely that your investigation team will be looking for DNA to collect and use to solve the case.


Processing Blood Samples, FBI
Forensic analysis of DNA can be confusing so let's walk through this together.

STEP ONE - What Is DNA? 

First the bilology basics. I know. I know. It's the spinach on your plate. But it's important, so I'll try to make this as quick and as painless as possible.


DNA - Deoxyribonucleic Acid -
* All cells have DNA (except red blood cells)
* DNA is the genetic material making up our chromosomes
* Gene – the basic unit of heredity; a sequence of DNA nucleotides
   on a chromosome.
* Genome – the sum total of an organism’s genetic material.
* DNA encodes the instructions for when and how to make
   proteins. These proteins tell the cell how it will
   function - is it a brain cell? a liver cell?
* It looks like a twisted ladder. The uprights are made out of
   phosphates and sugars. rungs are pairs of
   smaller particles called nucleotides.


You're doing great! Hang in there!


English: DNA replication or DNA synthesis is t...
(Photo credit: Wikipedia)
* All DNA is made up of a combination of four letters
  G - Guanine
  C - Cytosine
  A - Adonine
  T - Thymine
* G and C got together A and T go together
Happy Valentines Day - Relationship Mitosis
Mitosis (Photo credit: id-iom)

Mitosis -
* DNA replication
* A cell splits by dividing like a zipper
* The new cells contain an identical set
   of cells as were present at conception
* This only changes when there is a
    random mutation
* All cells in the whole body contain the
   exact same DNA

Video Quick Study of Mitosis (1:29)
VIDEO QUICK STUDY (8:03) basic info on DNA and Mitosis - might be more information than you need, but the presentation is thorough and easily understood.


STEP TWO - There Are Two Kinds of DNA
Prokaryotes are primitive cells, without a nuc...
 (Photo credit: Wikipedia)

Nuclear DNA-
* It is found inside the nucleus packed
   into chromosomes
* It is inherited from both parents
   50% from our mom and 50% from
   our dad.
* Each parent contributes 23
   chromosomes for a total of 46.
* The dominant and recessive qualities
   gives us our traits
* A DNA profiles belongs to an
   individual and ONLY that
   individual and no one else in the world    UNLESS we have an
   identical twin. Plot twist!
* The closer we are in genetic
   relationship to someone else, the
   closer the DNA configuration.
* Each cell has one copy of nuclear DNA


Mitochondrial DNA-
* Is found in mitochondria
* 100% of mitochondrial DNA is inherited from mom.
* The mitochondrial DNA is the same in our brothers and sisters
    regardless of who fathered each child.
* All mitochondrial DNA came from your mom which came from 
   your mom's mom which came from your
   mom's mom's mom etc. How cool is that?
* Is not housed in a a set of chromosomes
* This DNA is smaller than Nuclear DNA
* This DNA is present in larger numbers than Nuclear DNA
   (nuclear DNA has just one copy per cell)
* This DNA tends to be more stable than Nuclear DNA over time.

VIDEO QUICK STUDY (1:58) Two Minute Science Lesson: How DNA Testing Works

STEP THREE - Collecting DNA Evidence

Maryland V. King Police can collect DNA without a warrant Video Quick Study (1:55)


Biological evidence is perishable
* DNA will fragment
* The best shot at getting useful DNA is in a fresh sample
* Fresh tissue has more nuclear DNA and an older sample has less

Things that cause DNA to degrade

* UV light
* Acid
* Bleach
* Hydrogen Peroxide
* High humidity
* Heat and Fire
* Anything that oxidizes biological molecules


Handle with Care:
Video Quick Study (2:16) Mentions the changes in technology and the importance of properly preserving the sample.

* If the evidence that is being collected is wet it should be air dried.
* The evidence should be stored in a PAPER BAG that can release
    moisture
* Store in low temperatures (this prevents bacterial or fungal
   growth that has its own DNA)
*  Avoid as much as possible environmental contamination.

Crime Scene Techs:
* Need to understand that they can be contaminated by the crime
   scene (pick up bacteria etc.)
* Can contaminate a crime scene with their own saliva, dander, hair
   etc.
* The FBI Processing unit that I visited this week uses full Tyvek
   suits to prevent contamination of the scene.
* People who were on the scene will often be asked to give a DNA
   sample called an "ELIMINATION SAMPLE"
* Most often reference samples are taken from a buccal swab. A
   square piece cotton is swabbed over the
   inner cheek. This is placed in an envelope. Why not a vial?
   Because a closed container encourages the
   growth of other life forms. 
   VIDEO QUICK STUDY (3:07) How to collect a buccal sample.
* DNA elimination samples are collected from victims and
   witnesses etc.




English: A forensic scientist at the U.S. Army...
. (Photo credit: Wikipedia)

PLEASE NOTE this elimination sample does NOT get run through the system. It is merely there for the scientists to compare with the sample they are analyzing. Your character will NOT be located and charged with a previous crime. There are all kinds of privacy laws that prevent this from happening, according to the FBI agents we were interviewing.


Death Investigators: What if you have a body to identify?
If the investigators have an idea who this might have been they can get a swab from a blood relative and try to find markers that they share. If no relative is available, then they could go to the person's home and try to collect DNA there from a toothbrush or razor, etc.

What if the house burned down and DNA from that location is not available? Well, investigators could try to find stored DNA samples, for example a woman's pap smear might be stored or perhaps your character had given blood to the Red Cross.

Here's a VIDEO QUICK STUDY (6:09) that gives a simplified description - good overview. 
STEP FOUR - Extracting and Processing DNA

Extracting DNA isn't hard you can do it right now in your own kitchen. Don't believe me?
Video Quick Experiment for You to Try (2:46)
Video Quick Study - Separating DNA from Blood (6:37)

In extracting DNA from Crime Scene or reference samples, the goal is to find the 1% that differs from everyone else. This gives an individuals DNA Fingerprint or DNA Profile.

99.9% of our DNA is the same in all humans. Only .1% differentiates us


* DNA is stiff and brittle. In order to avoid damaging it, a

   technique is employed that breaks down the cell around it.
* In a crime scene laboratory being meticulous is paramount.
VIDEO QUICK STUDY - (6:19 - but go right to 3:00 mark) this
   process is better explained through this video than writing the
   steps because of the equipment

IF YOU ARE WRITING A BOOK THAT TAKES PLACE IN THE 80s OR 90s use RFLP:


RFLP Analysis - Restriction Fragment Length Polymorphism not widely used since the mid-90s
* A large sample is required
* Results are not compatible with major DNA databases
* The proces uses molecular scissors to cut where a TA next to a
   CG combos. Since everyone has different DNA profile's the
   material created will be of different lengths. (15-35 repeating
   base pairs)
* This is then processed with Gel Electrophoresis
   Video Quick Study (5:18) Frankly this is the quickest, easiest
   way of understanding the process

To correct the problem of sample size, scientists developed PCR - Polymerase Chain Reaction
* This was developed in 1983 as a method for replicating DNA
VIDEO QUICK STUDY (3:32) sorry this has no audio, but it is
   the best quick study I could find
* PCR takes advantage  of the DNAs double strand and its simple
   code
* Uses a thermocycler to double the amount of DNA with every
   cycle.
* Only one strand of DNA can make a billion copies in four hours

IF YOU ARE WRITING A BOOK THAT TAKES PLACE AFTER Mid-90s use STR:

STR - Short Tandem Repeat
* It still uses PCR to make copies
* STR focuses on the smaller repeating units in DNA
* STR uses only about 3-7 repeating base pairs (where RFLP
   needed 15-35)
* Can be used on much smaller samples than RFLP
* Can be used on more degraded samples than RFLP
* Only 18 cells are needed to get a DNA profile - this is why they
   can pick up DNA from a fingerprint, according to our FBI
   instructor.
* Uses Capillary Electropheresis -  done in a column (not in a flat
   gel as in electrophoresis)

THERE ARE 13 DIFFERENT CORE LOCATIONS WITHIN DNA that captures most of humans variability in STR


CODIS FBI Logo
CODIS FBI Logo (Photo credit: Wikipedia)

* Each core location has its own
   established probability of being
   found in the larger population.
* When all 13 different probabilities
   are added together the statistical
   probability are in the quadrillions.
* These can be put into the CODIS
 (Combined DNA Index System)
  developed by the FBI in the late
  90s. Pay attention to this date if
  your story happens before this time
  period.


Recently they've developed a way to tell if the DNA comes from a man or a woman by looking at the sex chromosomes. (XX or XY) They do this by looking at the amelogenin gene on the sex chromosome. It is longer in a man than woman but this is enough to tell the difference. This is important because sometimes there is a mixed sample of DNA, for example if they do a vaginal swab for sperm.


STEP FIVE - Is It a Match?

Reading the computer output is outside of the scope of this article - though I will address this in the near future.


CODIS 13 point profile
CODIS 13 point profile (Photo credit: Wikipedia)
The information gathered is analyzed and a statistic is assigned.
Population Genetics gives us
    statistics about the likelihood of this
    profile occurring in a population. It is
    a PROBABILITY that the same
    profile is replicated in the population
    and not coincidence.
* The more stretches of DNA that are
   compared between two people the
   statistics possibility of error narrows.
   It can become so narrow that it
   EXCLUDES everyone
   else from the pool of possibilities
   EXCEPT an identical twin.




Okay how was that? Not bad right? We made it to the end of the DNA pathway. Now as you sit on the bench to catch your breath, let's review some points at which a plot twist could mess everything up:

* Has the prosecution kept tight control of its chain of who has
   custody from collection to end result?
* Was the biological material from which the DNA was extracted
   identified? For example, in a rape case was it semen that is being
   identified?
* Is the testing laboratory accredited?
* Has the testing laboratory  been audited by an outside agency?
* Has the testing laboratory  undergone a proficiency test - and was
   it a blind test?
* Did the laboratory run the required control samples?
* Was there examiner bias? Did the tech talk directly to the
   investigator or was it blind?
* How large was the DNA sample? Was it from a pool of blood?
   Or was it from a fingerprint?
* What if your character -- either victim or accused -- has a relative
    involved in the research (or an ex-wife eek!)?
* Was more than one DNA profile mixed in the sample?

So many ways to play with DNA evidence! 



EDIT 
Intermountain Forensics:
This is very good! If we could add to your collection: CODIS Core Loci is now 20 markers and keep an eye out on next generation sequencing and genetic genealogy for the future of forensic DNA. Nice work!

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