Showing posts with label Crime scene. Show all posts
Showing posts with label Crime scene. Show all posts

Wednesday, March 19, 2014

Forensic Trace Evidence: Hair and Fur - Info for Writers

 (Photo credit: Wikipedia
So your investigator arrived on the scene.
(Crime Scene 101 for writers article)

They've photographed and collected all of the macro-evidence. 

Now they need the trace evidence (that which isn't easily seen with the naked eye) collected and processed. This trace evidence might include hair. 
* Hair is one of the most collected forms of trace evidence.
* Hair is particularly useful because it is stable over time.
* Because hair is produced around blood vessels it is a long term
   record of toxins
   ` Illicit drugs such as THC in marijuana
   ` Poisonings such as arsonic
   ` Heavy metal exposure such as lead.
   ` Medications
* Hair grows at a fairly predictable rate of about .5 inches per
   month. So scientists can even calculate when the exposure to
   the toxin began - depending on the length of the hair.

Investigators will use three basic means of collecting hair and other trace evidence.

1. Hunt and peck
2. Tape
3. Vacuum
Video Quick Study (9:50) Prt 1 
Video Quick Study (1:54) Prt 2 Teacher explaining collection
                     methods of finding trace evidence including hair. 

Humans have various hair all over their bodies including body hair, eyelashes, and eyebrows. But only head hair and pubic hair have forensic use.

So let's say we have a rape victim. They find hair on her clothes. 
1. They will have to collect hair from the victim - this is a known or
    K sample
2. The laboratory will compare the victim K sample to the 
    Q sample - the sample in question.
    a. First, they will figure out if the Q sample is a human hair.
    b. Second, They will determine if the K and Q samples have
        the same general characteristics.

Let's say that the victim K sample excludes the Q sample that is they could not come from the same person. But our investigators have their eye on a bad-guy. They ask him for hair samples. He can 
a. Agree and submit to testing
b. Refuse - if he refuses then the courts can order him to submit.

The suspect K sample is collected.
1. It is suggested by the FBI that 100 full, intact strands, including
    the follicle are harvested from the suspects head from various
    regions as even hair from an individual person can differ
    from region to region on their heads.
2. It is suggested that at least 20 intact strands of pubic hair are

*If the laboratory says that the suspect K sample and the Q sample
  do not share similar qualities, this excludes the suspect. 
*If the lab says that there are similarities in the K and Q samples,
  this DOES NOT mean that you found your villain. 
* Hair is class evidence - it can be used to exclude but not to prove
   someone is culpable.
* If there are similarities, the sample is sent for DNA testing.
  (DNA 101)
* By doing lab analysis first, it saves a great deal of time and money
   over going right to DNA analysis

Let's do a little biology 101 - I know you're excited!

hair follicle
(Photo credit: Wikipedia)

* The root of the hair is
   anchored into the dermis of
   the skin
* Follicles are surrounded by
   epidermal cells
* Blood vessels at the roots
   deliver nutrients

Looking at the hair itself

* Hair is mostly made
   from keratin
Haarstrukturen im Vergleich
 (Photo credit: Wikipedia)
* The outside of the hair is 
   called the cuticle
* In humans, the cuticle
   gives very little information. 
* Mammals have various
   patterns in their cuticles and
   the labs can compare the
   various patterns to tell
   that's a bat, or a rabbit, or a

* Inside of the cuticle is the cortex.
* The cortex is the thickest layer of the hair strand.
* This is where pigment from the melanin can be found, giving hair
    its color.
   ` Hair colorant can coat the surface or penetrate to the cortex.
   `In bleached hair pigmentation is lost from the cortex
   `Only the hair that is treated will show a change in color, so at the
     root the true color will be visible. There will be a line of 
     demarcation between the two

* When people change the color of their hair, or their hair changes
    naturally as the subject ages, this can create issues in finding 
    similarities in the K and Q samples. 
   A fingerprint cannot be altered, but your villain can thwart an
   investigator by dying their hair, committing a crime,
   and then dying their hair a different color. So even if the police
   take K samples from their hairbrush they will not show as similar
   in the lab. And when they take them from hair that's been altered
   it too will not show as the same.

Photomicrograph of Pubic Hair Medulla
Pubic Hair Medulla (Photo credit: Wikipedia)
The Medulla
* The medulla is at the core of the hair sample
* It is the hollow region at the center.
* A data bases of medulla patterns have been developed to
   identify various animals and differentiate human from other
   animal hair.
* Finding animal hair can be very helpful. It can link transferred
   hair from a suspect at a crime scene. For example, Blade Slayer
   goes in and attacks your heroine. Trace evidence hair is found.
   It's a black rabbit, and Blade Slayer happens to have a black
   rabbit named Cuddles. It's circumstantial, but it can be helpful.
* Animal hair forensics can also be used in crimes like poaching
   and illegal animal importation (Wildlife Forensics Blog Post)

Three Phases of Hair Growth

Anagen Phase
* 2-7 yrs for scalp hair 
* Growth phase where cells are formed at the root which pushes the
   hair out of the scalp making the hair longer.
* This hair will only fall out if it is yanked out.
* When hair from this phase is
Animation of the structure of a section of DNA...
Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands. (Photo credit: Wikipedia)
   found at the crime scene it has a
   follicle attached. 
* The follicle contains DNA that
   will identify an individual
Catagen Phase
* The hair is in transition
* The hair no longer grows, the
   cuticle pulls away
Telegen Phase
* The final phase where hair falls
* In the catagen and telegen
   phases the follicle is no longer
   attached to the hair. Nuclear
   DNA cannot be found. The
   investigators will try to test for
   mitochondrial DNA in the hair
   shaft. Mitochondrial DNA is not
   conclusive as everyone in the
   matriarchal line will have the
   same DNA (DNA 101 for Writers)
* Telogen hairs are those typically found at crime scenes.
* Because hair is easily transferred from one place to another, it is
   circumstantial evidence.

What else can an investigator tell from a hair strand?

* Pubic hairs have shaft differences along the length and a
   continuous medulla
* Male facial hair is usually more triangular in shape
* Hair that's been cut or shaved will have a blunt end
* Hair that is allowed to grow naturally such as arm hair will have a
   naturally tapered end
* Head hair - not recently cut- will show a frayed or split end
* Age cannot be discerned.
* Sex cannot be determined.
* Ethnicity - is difficult. The person would have to have a very
   clean background as Caucasian, African, or Asian ancestry.
   And then, there are variables that can point the investigators
   in a direction. It is not conclusive.

So what can an investigator say about a hair sample?

* Is it human, or animal (or vampire)?
* Is it a useful sample, either head or pubic hair?
* Is it head or is it pubic hair?
* Is the Q sample consistent with the K sample?
   `If yes, further investigation - suspect stays in the pool.
   `If no, suspect is removed from possibilities; they look for another
   `If yes AND no that is there are similarities AND differences,
    then no conclusion can be drawn.

Video Quick Study (4:16) Hair testimony at Casey Anthony trial
Video Quick Study (4:27) Britain CSI school

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Monday, October 7, 2013

Crime Scene 101 for Writers: Decisions. Decisions.


 (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.


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
* Others who enter a crime scene can introduce
   Finger prints Link to finger print article
   Foot prints Link to footwear article
   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, July 22, 2013

Bullet Tutorial for Writers

.40S&W cartridge next to expanded hollow point...
.40S&W cartridge next to expanded hollow point bullet. (Photo credit: Wikipedia)
DISCLAIMER - This is a non-political site that is geared to help writers write it right. I am presenting information to help develop fictional characters and fictional scenes. In no way am I advocating any position or personal decision

So things got pretty serious. Guns were drawn; a body sprawls on the ground. What the police find on the scene has a lot to do with what kind of bullet you as the author chose for this plot line.

If you need a tutorial about Step One - choosing a gun click HERE

Once your heroine has a gun in her hand, there are other things to consider. Let's begin understanding bullets and how they impact plot.


* The bullet is just the top piece of the round - the part that hits the
* A cartridge or round is the entire component 
   (brass + powder + primer) When the primer is hit by the hammer 
   or firing pin, it ignites the powder in the shell, forcing the bullet 
   in the only direction it can go - down the barrel of the gun.
* The caliber is a measurement of the bullet. (If the bullet has two
   numbers the first is the width of the bullet the second is the
   length of the round.)
* Another way to measure a round is by grain the higher the grains
   the more the bullet weighs - the slower it goes and the deeper it
   will penetrate.

INTERMEDIATE - How to read a bullet box:


*Full Metal Jacket (FMJ) - the entire case is encased in metal,
  offering the most penetration through your  target. The base is 
  exposed showing the lead.
*Total Metal Jacket - (TMJ) - The entire case including the base
  is covered
*Semi-jacketed (SMJ)- or just (J) for jacketed - the jacket only
  goes half way up the bullet.


.22 hollow point     9mm hydro-shock      9mm FMJ round nose/tip

Flat Point - (FP) has a flat tip (pictured below - left)

Round Nose - (RN) (below center) - This bullet will not expand in
      size with impact; it will continue on its trajectory. 

      This is an author's decision if she wants the victim to have an 
      exit wound, to die of impact/blood loss, or for the bullet to hit a
      secondary object or person. All of these would could result
      from a RN Click HERE to go to my blog article on Blood
A cut-through of a hollow-point bullet. The pr...
A cut-through of a hollow-point bullet.  (Photo credit: Wikipedia)

Hollow point -(HP) the tip is hollow. When it hits its

      target it will expand very quickly to almost 3x it's 
      original size. This means that the bullet expresses 
      the power inside of the body, damaging more 
      tissue than a round nose bullet. This expansion 
      also reduces the chance of a bullet exiting the 
      body and hitting someone nearby. This is safer 
      for self defense where innocent people are 
      nearby. This type of bullet creates massive pressure
      and the victim is likely to die of a brain embolism.
      Click HERE to go to my blog article on EMS and
       gunshot wounds.

Video quick study: First Science TV Round Nose v. Hollow Point (2:08)

Author's own picture. 9 mm pistol cartridge

9mm flat tip                     9mm round tip                    9mm hollow tip
 (Photo credit: Wikipedia)

ADVANCED - Information about calibers

Baby Bear

.22 is cheap so it's good for target practice, but has minimal penetration - not great for defense.

Video Quick Study (5:56) This is a little in depth but shows him weighing the bullet (grains) and measuring the bullet for caliber, and also ballistic tests through testing medium.

.25 is used in small pistols it has a big kick - so a lot of recoil.
.32 penetrates a little deeper than a .380 and has less recoil  
.25 for a very small gun this is a good self-defense round

Mama Bear

38s and 9mm are the same size bullet. One is calculated in inches, and one is calculated in metric.The three kinds of 9mm  from smallest to biggest:

.380 Auto vs. 9mm Luger
.380 Auto vs. 9mm Luger (Photo credit: Wikipedia)
.380 and 9mm Short are the
   same (9x17) a little more
   power than the 38 special - 
   goes in a small pistol.
* 9mm Makarav (9x18)
* 9mm Luger is also known on
   the box as a
   9mm Parabellum (9x19)
   These are accurate far
   away, up close they are devastating. At 15 to 20
   feet your character might have to hit a guy 6 times
   to stop him if he's drugged up.
   (This is the bullet I shoot in my Springfield)

This is probably as big a caliber as your character needs. But if you are trying to make a decision between giving your character a 9mm or a .45 here is a good comparison video
 9mm v .45 bullet (17.31)

Papa Bear

.40 is the same as a 10mm. But a 10mm is really a .40 caliber magnum (I'll explain in a second) The .40 does not have the penetration of the 9mm because it is heavier and takes more power to shoot.

.45 is highly effective in dropping the target in one shot.

Video Quick Study: 10mm ammo energy test   (7:28) go to 3:50 mark

Rabid Klondike Mama Bear Protecting Her Young -or-What is MAGNUM?

A magnum round is a high powered round. So for example you can have .22 magnum or .45 magnum
* Lots of recoil
* Painful to shoot
* This is for hunting (a back up when an angry bear is running full
   tilt at the heroine) not usually for self-defense.
   The gun must be designed to handle magnum bullets unless of
   course you want your heroine to put a .44 magnum (name of a
   round) or .44 special (name of a round) and blow her gun apart
   because the gun couldn't handle the pressure.

Popular wisdom says, a bullet shot from any handgun at a distance of three feet will probably stop anyone. Most of the time a civilian is shooting, it is that close in range. Stopping power is not as important to a civilian as it is to a police officer whose range moves out to nine yards. So your gun/bullet choice depends on who is doing the shooting and why.

Sonic v. Subsonic Bullets Shot with a Suppressor - 

Brian Coates, U.S. Marine Corp., veteran

LINK Nottoway Shooting Sports

PLOT TWIST - One thing that I should point out is that just because a bullet will load into the gun, it does not mean that there will be success in shooting it. A particular round might misfire or jam. Once you know which gun is being used, research which bullets work best. Though, this could create a plot twist for you. Perhaps your heroine is new to the gun scene and buys a weapon for self-protection, purchases some bullets, loads it all up and there is a catastrophic failure. She could be hurt instead of the villain.

Image publicly distributed source unknown

VIDEO 1 - Bullet Basics 101 (8:01)

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.

Tuesday, March 19, 2013

Footwear Evidence for Writers – by Patti Phillips

Conferences are a blast for the mystery/thriller writing crowd these days. And not just because of the workshops improving our craft and technique providd by the many writing organizations. I appreciate those I do. But for all-out, slam-dunk fun, I go to the Writers' Police Academy (founded by Lee Lofland). It’s a three day, hands-on, mind-blowing experience that demonstrates the nuts and bolts of police and fire and EMS procedure – taught by professionals and experts actively working in the field. All with the purpose of getting writers to improve their technical knowledge so that they can get it right on the page.

Along with several other strands of study, the last two WPA conferences provided classes in bloodstain patterns, fingerprinting, and alternate light sources (ALS) conducted by Sirchie instructors. Because of the standing room only enthusiasm for these classes, Sirchie offered a five-day Evidence Collection training session for writers at their own complex in North Carolina. Sirchie makes hundreds of products for the law enforcement community and I felt this would be a great opportunity for Detective Kerrian (my protagonist) to learn more about the latest and best gadgets being used to catch the crooks.

Wolverine cast

Criminals rob, murder, rape or otherwise inflict bodily harm upon their victims. Physical evidence at a crime scene is an essential part of figuring out what happened. It is up to the police officers, investigators, and examiners to recognize what is and is not part of the evidence and then interpret the importance of each fiber, fingerprint, bloodstain, and other material in order to secure a conviction of the correct individual.

One of the most overlooked pieces of evidence at a crime scene is created by footwear.

If a window breaks as a thief enters the premises during the commission of a burglary, the glass will fall into the house, and onto the floor or rug below the window. When the thief steps through the window, unless the thief has wings, he/she will probably plant a foot right in the middle of the glass. And walk through the house, most likely tracking minute pieces of that glass. That glass may also become embedded in the grooves of the sole of the shoe, creating a distinctive footprint.

If the investigating officer can place a suspect at the scene with the footprint, then there is probable cause to fingerprint that suspect and hopefully establish a link to the crime.

A new method of eliminating suspects right at the scene involves stepping into a tray that contains a pad impregnated with a harmless clear ink that doesn’t stain, then stepping onto a chemically treated impression card. (So safe that it’s often used on newborn babies for the hospital records) No messy cleanup, immediate results, and it can even show details of wear and tear on the shoe. This can be a way to establish a known standard (we know where this impression came from) to compare with multiple tread prints at the scene.

Footwear Clear Ink Impression

Another tool for creating a known standard is the foam impression system. It takes a bit longer, (24 hours) but clear, crisp impressions can be made, including of the pebbles and bits stuck deep into the grooves and the writing on the arch. Very helpful when trying to place suspects at the scene. A rock stuck in the sole is a random characteristic that can’t be duplicated, so becomes another point of identification.

We definitely wanted to try this method for ourselves. Each of the writers stepped into the box of stiff-ish foam – a bit like stepping into wet sand.

Using foam impression system

An impression is made instantaneously. Look at the detail – down to the wear on the heel.

Foam impression of Wolverine boot

We used pre-mixed dental stone (made with distilled water and the powder) to fill the impression.

 Making the cast with pre-mixed dental stone

We waited 24 hours for them to become firm enough to pop out of the foam. We now had permanent records of the footwear treads, which could be used for comparison to other prints found at the scene. There were more than a dozen of us walking through that room every day on a regular basis and assorted other visitors tramping through the perimeter. If a crime occurred before we left for the week, we’d have a LOT of eliminating to do, but we were ready!

Photo: Footwear casts

Occasionally footprints are found on the ground outside a window or in the gardens surrounding a house after a burglary or homicide. Ever see a crime show on TV  where the fictional investigator makes a snap judgment about the height and weight of the owner of the footprint because of the depth of the impression? That’s merely a plot device and is not scientific evidence in real life. A crime scene photographer or investigator can photograph the footprint (next to a measurement scale), make a take away cast, and then compare the impression with those of the suspects or other bystanders at the scene. Beware: making a cast of the print destroys the print, so a photograph must be taken before pouring that first drop of dental stone.

Footprints can be found at bloody crime scenes as well. The suspect walks through the blood, tracks it through the house, cleans it up, but the prints are still there, even though not obvious to the naked eye. As we learned during the ‘Blood and Other Bodily Fluids’ session, blood just doesn’t go away, no matter how hard you try to get rid of it. It seeps into the cracks and crevices of a floor and even behind baseboards.

A savvy investigator will collect sections of carpet (or flooring) taken from where the suspect might have walked during the commission of the crime, then conduct a presumptive test for blood (LCV - Aqueous Leuco Crystal Violet), find a usable footprint, compare it to a known standard, and then be able to place the suspect at the scene.

Footwear Print

Kudos to Robert Skiff, the Sirchie Training Manager/Technical Training Specialist who conducted the classes with his assistant, Chrissy Hunter, all week. He fielded our many (sometimes wild) questions with solid expertise as we attempted to find the perfect scenarios for our fictional crime-fighters and criminals.


Patti Phillips is a transplanted metropolitan New Yorker/north Texan, now living in the piney state of North Carolina. Her best investigative days are spent writing, cooking, traveling for research, and playing golf. Her time on the golf course has been murderously valuable while creating the perfect alibi for the chief villain in “One Sweet Motion.”

Did you know that there are spots on the golf course that can’t be accessed by listening devices? Of course, it helps to avoid suspicion if you work on lowering your handicap while plotting the dirty deeds.

Patti Phillips writes the blog and the book review site

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