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

Wednesday, January 21, 2015

TOXIC: Information for Writers from Forensic Toxicologist Sabra Botch-Jones



Today, ThrillWriting welcomes Sabra Botch-Jones. Sabra is a Forensic Toxicologist and full-time faculty member at Boston University School of Medicine’s Biomedical Forensic Sciences graduate program. She teaches courses in Drug Chemistry, Forensic Toxicology and Instrumental Analysis in Forensic Laboratories.

Fiona - 
Sabra Botch-Jones, M.S., M.A., D-ABFT-FT
Department of Anatomy & Neurobiology
Boston University School of Medicine
Biomedical Forensic Sciences
Sabra, you have a very cool title. At what point did you realize that you wanted to be a forensic toxicologist?

Sabra - 
I realized that the field of Forensic Science was “where” I wanted to be in during my junior year of my undergraduate degree when I took an Introduction to Forensic Science course. I “thought” I wanted to be a psychiatrist. I did not know that the sub-discipline of Forensic Toxicology was my calling until I was working as an intern at the Federal Aviation Administration during my final year of undergrad.

Fiona - 
Here is a PRIMER on Forensic Toxicology.

Can you tell us what a forensic toxicologist does?


Sabra - 
A forensic toxicologist is like a chemist. We conduct instrumental analysis on biological samples (like blood and urine, but also body tissues or even bone at times) to determine the presence of drugs, including alcohol, and sometimes other compounds (like heavy metals, etc.) 

We are also trained in the interpretation of those results and what they may mean based on the case we are working with. For example, a toxicological result in a living person such as a Driving While Impaired (DWI) case may be different if we find the same value in a deceased person.

Forensic Toxicologists can work in Federal, State, County or private laboratories. The cases can involve living and deceased individuals.

Fiona -
You're sitting on the couch in your den, enjoying a bowl of popcorn with some of your colleagues and watching TV - a crime show. What are the things that make you throw food at the screen and yell at the writers for getting it ALL wrong? What points do you want writers to pay the closest attention to so that you can enjoy the plotline?

Sabra - 
So, I don’t have a lot of time to watch TV. As the mom of a 2 year-old, I watch a lot of Curious George (which I love); therefore, I don’t get to watch a lot of crime shows. But if I do, the over simplification of some things and the time it takes drives me crazy.

I don’t let it get to me too much because I know the producers and writers are working with time constraints to tell a story. Plus, as Forensic Toxicologists we are always trying to reduce the time it takes to perform analysis so at times it makes me wistful for faster analytical times. 

There is one other humorous thing forensic toxicologist like to joke about and that is wearing white clothes in the laboratory. Besides our lab coats, we don’t typically do that, but now I do it on purpose because every time I do I think of a shows like CSI.

Some points that would really impress me would be using the difficult names of our instrumentation like Liquid Chromatography Tandem Mass Spectrometry or Supercritical Fluid Chromatography.

Fiona - 
Do you ever go to a crime scene? Do you ever interview a witness or a family member? Do you ever seek (outside of the laboratory) evidence to support a theory that you came up with while doing your forensic analysis?



Sabra - 
Those are good questions, because the typical answer to that question would be no. Most Forensic Toxicologists stay in the lab and are very happy to do so. But, I have been very fortunate in that during my career I worked in a medical examiner’s office with a Forensic Anthropologist who needed help in recovering skeletal remains. Therefore, I have been to scenes -- some were and some were not crime scenes. In one instance, we actually found drug paraphernalia. I do not interview witnesses or family members, however I have spoken with individuals who believed they were being poisoned or victim’s family members to address their questions and concerns.

Also, depending on the laboratory, we may conduct experiments to determine why something happened. One of those areas as a Forensic Toxicologist would be to recreate storage conditions to determine analyte stability.


Fiona -

With whom do you interface? How do the samples get to you? 

Sabra -
We interface with medical examiners, attorneys, police officers, judges, jurors, and at times family members. Depending on the laboratory, samples may be hand delivered or may be sent to us. 

Fiona - 
From whom do you get information for what you are looking for in the sample? Do the detectives ever sit down and chat with you about the case and their theories/what they are trying to prove?

Sabra - 
Case information comes in a variety of different ways. If medical information is available for a case, we would review it. We may also look at the investigators' narratives and police reports. Some police officers go through extensive training to become Drug Recognition Experts, and their reports can be very useful. Police officers or investigators do not usually discuss their cases with us, unless they need interpretation on what the results mean. They may want to understand what a drug is and what its effects would be. We don’t typically get involved in the “proof” of a case, as our role is that of a scientist or “fact finder”.

Fiona - 
Let's talk plot twists. If a sample is collected -- at the scene or a hospital, for example -- and it is properly packaged for clean chain of custody. Is there any way that a character could taint your sample or switch your sample or for that matter change your report to reflect something other than what was found? The presence of drugs for example?

Sabra -
As a plot twist that's a fun one but a nightmare in reality to a Forensic Toxicologist. 

The purpose of chain of custody is to preserve and protect the evidence. But for this example, we don’t have to look too far for real life examples of mistakes that have been made. Storage is one, let’s say you have an unstable analyte that must be kept at a certain temperature or it begins to degrade. Leaving a sample locked in the back of police car (intentionally or unintentionally) might have deleterious effects.

Another scenario would be switching out a sample before or at the lab such as having an “insider” or a “break in” at the laboratory. These all make me shudder but are reason why we have so many safeguards and security measure in our laboratories.

Fiona -
Have you been to court as an expert witness?

Sabra -
I have been to court as an expert witness and I have interacted with both the defense as well as prosecutors. As a Forensic Toxicologist in government laboratory I primarily dealt with the prosecutors or District Attorney’s office. As a consultant, I have dealt mainly with the defense. The hearing was fairly straight forward.

Fiona - 
What was it like to sit in the witness box? Did the defense lawyers try to rattle your cage?

Sabra - 
I have had attorneys try to rattle me before I took the stand so that I may not present myself in the best possible way. The witness box is a very important place to be and I believe an individual who has the opportunity to sit there should show it the respect it deserves. 

Fiona - 
Can you give examples of defense rattling techniques? That's good plot fodder.

Sabra - 
I had the opportunity to do an interview for The Setup (you can find my interview here: http://sabra.botch-jones.usesthis.com/) and the image I provided was one of a flask and cocktail glass held up to my face. This image represented what we do as Forensic Toxicologists, looking for chemicals that enter the human body. I had an attorney show me the image before testifying and during the cross-examination. I believe he wanted to rattle me, but when he asked me about the interview I had the opportunity to talk about what we do as Forensic Toxicologists and the technology we use. 





Fiona - 
I always ask my guests to share their favorite scar story or lacking scars their favorite harrowing event story. Would you share?

Sabra -
I have been very lucky to not have many scars, but the ones I have I wear with pride. The longest was from an emergency C section for my son (I also have a couple on my face from him when I let his nails get too long). I am really fortunate to not only get to be a mom but also a scientist. It’s a tough balance, but being a mom, I think has complimented my new role as an educator of future Forensic Toxicologist and Forensic Scientists.

Fiona - 
Where could an author look for new material - what's being explored in forensic toxicology?


Sabra - 

One of my research focuses include New Psychoactive Substances, and I think this is a great area to explore for writers. Not just the use, but how they are made and obtained.

Fiona -
Sabra, thank you so much for helping us writers out. I truly appreciate your time and expertise.

You can stay in touch with Sabra on  Twitter
fTox Consulting, LLC. website
BU faculty website


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.


Wednesday, June 11, 2014

Tool Mark Forensics: Information for Writers



English: Box with tools. I took this photo dur...
. (Photo credit: Wikipedia)
Your investigator is on the scene, looking for any clues that could get the villain off the streets. 

Maybe the villain was smart enough to wear gloves, but was he smart enough to buy a new tool and make sure that it was destroyed afterward? 

No? You might just have written a plot twist. 

Imagine if the perpetrator was trying to set someone else up with the crime. The villain borrows the hero's tools, and then carefully puts them back in the hero's garage and phones in a 1-800 tip to the police, sending the authorities to your hero's home with a search warrant in hand. 

This would be especially damning if the only prints left on the tools were the hero's. Can he talk his way out of this? Did he have an alibi? Or is he  now in jail leaving your intrepid heroine to carry on without his help?

Crime Scene 101 article
Warrants Blog Article
Finger Prints article

Types of Tool Marks Left Behind

* Shape of the tool
* Random microscopic irregularities and imperfections produced in
   manufacturing. These are frequently invisible to the naked eye.
Wear-use - as a tool is used over time it develops new and unique
   features such as abrasions and erosion of the surface which is
   more likely to be visible upon inspection.


Wear Use on a Tool

* Wear-use takes place prior to the crime but can also be altered as
   the criminal uses the tool during the crime. 
* The wear use can help a forensic scientist make a match and
   show a probability that the investigators had found the right
   tool/weapon. 
* Unfortunately, this can also work against investigators should the
   tool not be found immediately and the tool is then used elsewhere
   and changed.


Information Left by a Tool


English: Standard Hammer
 (Photo credit: Wikipedia)

The forensic scientist will determine the class of weapon. Class of weapon simply identifies the general tool - was it a screw driver that gauged the hole in the window frame? Was it a saw that took out the balustrade?

When the tool leaves an impression then the scientists can
hypothesize about the tool - for example a round mark on the
wood indicating someone was swinging a hammer.



The forensic scientist must take three different surfaces into consideration when making determinations:
1. The tool
2. The surface that the tool interacted with. Obviously a machete
    attack on a mattress will have a different imprint than the 
    machete against a marble floor - though it will leave marks in
    both. So as you choose and implement your tool in your plotting
    consider the interaction with the contact material and what kinds
    of marks/information that you want to be discovered in forensics.
3. Use Edge - when a tool has an edge such as a shovel or pliers
    scissors etc. So for example, were scissors used to cut? Or were
    scissors used to bang? Or were scissors used to gauge?


Доработка Оптического микроскопа (File:Optical...
 (Photo credit: Wikipedia)

* No tools are identical
   because of microscopic 
   anomalies from
   manufacturing and use.




















Another idea that could inform your plot is the Locard's Principle

Locard said that whenever two surfaces come into contact one with the other there will be an exchange -
*If the tool is harder than the
  contact material then it
  might pick up materials like
  paint chips on the crowbar.
* If the surface is harder than the tool then the tool
   might leave trace evidence behind such as a car
   hitting a wall would leave the paint chips on the
   wall.
* Investigators should never try to fit a tool
   back into the indentation because it can
   alter the mark - so if you need a 
   wrench (*giggle*) thrown into your plot
   line you could have a newbie do just that.


English: A Park Tool crank extractor and cone ...
 (Photo credit: Wikipedia)

How is analysis done?

On the scene -
* Tools found at the scene are packaged and transported back to 
   the lab for research.
* Transportable surfaces are collected
   `A door can be removed
   `A portion of the surface can be cut and a portion collected
* Package each item separately so there is no cross contamination

In the lab -
* Test marks are make using the tool in question
* In the crime lab they will test the edge of a tool with a soft
   material - ex. lead
* After impressions are made into a soft material - then the
    investigators might try to replicate the strike into the original
    surface to see if the can match the strike/interaction
    (evidentiary marks).
* Duplication is difficult because of the pressure and angle of the
   strike
* The test marks are microscopically compared with the marks on
   the crime scene materials. This includes microscopic
   photography.
* Non-transportable surfaces are:
   ` Photographed with a ruler in place
   ` A cast is made - using liquid silicone or dental plaster - doing
     cast work is not ideal. The impressions do not allow for
     microscopic comparisons.

Video Quick Study (3:00) A forensic scientist mixing the Microsil, application and removal


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.




Thursday, April 10, 2014

Forensics in Your Plotline: Information for Writers



Amanda Knox reacts at the announce of the verd...
Amanda Knox reacts at the announce of the verdict of
her appeal trial in the Meredith Kercher' murder
 (Photo credit: Beacon Radio)
Amanda Knox has probably learned more about forensics than she probably ever thought or hoped she would. But her case in Italy makes a very interesting point. While specific laws change from region to region - country to country, what constitutes good science does not. 
Video Quick Study (1:26)
Video Quick Study (2:31) rape case thrown out over tainted forensic evidence


Forensics is a science; specifically, the application of science to the law. It is the application of scientific techniques developed through the scientific method that produces data. Are these 100% accurate and dependable results? No. They are not. They are within a scope or continuum - the data falls on a line of probability. When DNA results are offered, it usually reads as 98.99% chance of accuracy (and even those results are based on some pretty weird location generality tables). Nothing is 100%. This is an excellent way to twist your plot line.

I remember distinctly reading about a case where the body of a baby was hand-carried to the coroner for autopsy. Based on the coroner's findings, the mother was convicted of murder and sent to prison for life. Decades later when the officer was diagnosed with terminal cancer, he admitted that he had dropped the baby's body down a long marble staircase. Also, the person who had performed the autopsy had failed to document body damage that had occurred premortem versus postmortem. When these aspects came to light a second trial was held and the woman found innocent.

Forensics is processed by humans. Humans make mistakes. Mistakes effect lives - and plot lines.  

When you see a forensic scientist on the witness stand they will:
* Explain what they did in terms of collection and analysis and
   why (process)
* Offer an interpretation of the results (expert testimony)
* Explain how they arrived at their interpretations
* Explain what conclusions can and cannot be drawn. For example
   in the Casey Anthony case the forensic scientist indicates that
   hair is not a source of positive identification. 
    Video Quick Study (4:17)
   Video Quick Study (10:19) How reliable is forensic science?


Español: ESTUDIANTE INTEC
 (Photo credit: Wikipedia)

On occasion, forensics scientists will run experiments and try to collect data to help inform their testimony for a specific case.
Video Quick Study (2:10) 

And sometimes the scientists perform forensic experiments to inform future crime scenes. The Body Farm is an anthropological research center, for example, that sets up various scenarios for understanding how bodies decay. 
Video Quick Study (graphic in nature - 5:17) 


But it is important to note that not all forensic cases have to do with death. They can be anything from questioned document cases 
(Questioned Document Blog Article) to drug cases (Blog links to Illegal Drugs 101 and Toxicology Blog) and so forth.



Think about your crime scene as one great big science experiment.
1. There is an observation: "Hey, 
potd 4 17 12 - Forensic 497 final exam
potd 4 17 12 - Forensic 497 final exam (Photo credit: pennstatenews)
    look Harvey, I found
    a foot!"
2. There is a hypothesis: 
    "Someone must
     have been murdered!"
3. There is data gathering 
    (blog article CSI 101)
4. There is data analysis by
    various forensic experts
5. Conclusions are drawn. If the
    conclusion supports the hypothesis
    then you're ready to support a case in court. If the results do
    NOT support the hypothesis, then you have to start again with a
    different hypothesis.

Video Quick Study (7:33) Lack of reliable/valid research in forensic
                                          cases.

Here it is in a handy-dandy flow chart if that helps:


English: Flowchart of the steps in the Scienti...
 Scientific Method (Photo credit: Wikipedia)




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

When you are plotting your story, the analysis section is where you can twist the status quo. "The red toe-nail polish and dainty size did not hold up to DNA evidentiary review - this is not a woman after all!"

Now your inspectors have to start back to square one with the formulation of a different hypothesis.



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.


Wednesday, April 2, 2014

Wildlife Forensics - Information for Writers



______________________________________________________



Forest lake in summer
Forest lake in summer (Photo credit: Axel-D)
In wildlife forensics, an investigator attempts to tie a person or an object to a crime scene by using natural elements. These might include:
* Soil 
* Wood
* Pollen grains
* Animal hair (blog link)
* Animals
* Insects (blog link)
* Protists (single celled organisms found in water)




SOIL


Soil types
Soil types (Photo credit: Wikipedia)
Soil analysis might be able to link
* The shoes of a suspect (blog article: footwear evidence)
* Show where a car has traveled
* Show soil from where a victim was left.

Soil is made up of
* Inorganic - percentages of the combinations and make up of the
   soil differs from region to region so can help pinpoint an area 
   `rocks  
   `minerals (naturally occurring crystals)
* Organic
   `humus
   `decaying animal and bug matter
   `scat (dung)
* Man made 
   `glass
   `oil/gas
   `paint
   `Brick/asphalt

Who will test this information in the crime lab?
* Chemists
* Geologists
Video Quick Study (4:24) talks about using soil in Manson murder
Video Quick Study (9:11) soil samples might be analysed for poison
     and environmental crimes. 

Soils vary - 
1. Color
    Munsell System - describes the color of the soil
    * Chroma (purity of the color)
    * Hue - the color
    * Value - amount of white or black
2. Texture - like clay 
3. Particle size - measured through a graduated sieve.
4. Chemistry



POLLEN AND PROTISTS

Under a microscope investigators look for samples of pollen, protists
Scanning electron micrograph of Ipomoea purpur...
Scanning electron micrograph of Ipomoea purpurea pollen. (Photo credit: Wikipedia)

Palynology - the study of spores and pollen. 
Pollen and spores make good forensic evidence because - 
* They don't degrade easily
* Distinctive to a locality
* Help clue investigator to
   determine if the body was
   moved from one location
   to another

Protists
* Reproduce at certain times of the year - so they could narrow
   time frames.
   Ex. algae blooms in water
* If the body was in water or is suspected to have been in water,
   protists might be able to lead them to a specific location.
   SEM - scanning electron microscope

Video Quick Study (5:45) Pollen under the microscope and
     identification
Video Quick Study (1:50) Forensic botanist testifies at Casey
     Anthony trial
Video Quick Study (1:09) Forensic botany


WOOD

How is identifying wood helpful in an investigation? 
English: Pile of woods.
English: Pile of woods. (Photo credit: Wikipedia)

* Clues that might help
   identify a piece of wood
   `cut marks
   `nail holes
   `unique species
   `Species coming from a 
    distinct region
* Lindbergh baby abduction
   used a homemade ladder
   was left at the scene. The
   wood expert looked at the tool marks used to
   make the ladder and the different types of wood that were
   included in the construction
   Video Quick Study (3:28) Lindbergh wood expert



ANIMALS


An animal might 
English: Black bear
English: Black bear (Photo credit: Wikipedia)
actually be the suspect
* Perhaps the investigator
   is trying to determine
   which animal attacked a
   human.
* Diseased animals might
   cause attacks (such
    as rabies)
* Bite marks are examined
   by forensic odontologists
   (dentists)
   Video Quick Study (2:25) forensic odontologist at work
* Animals at large are tracked using the same methods
   as with humans (blog article: footwear)
* If the investigator suspects the animal that attacked/ate someone
   was found the investigators will examine the animal's stomach 
   contents.



English: Baby elephants in "The David She...
 (Photo credit: Wikipedia)


An animal might be the victim
* Abuse
* Poaching
   Video Quick Study (2:16) Wildlife forensic biologist
* Poisoning/baiting - tested by forensic chemists
* Hunting outside of the proper season or with illegal methods
* Illegal trade in protected wildlife is the third largest grouping of
   criminal activity following drugs and guns.
   ` Worth billions a year.
   ` Endangered Animals and Plants - Over 30,000 plant and animal
     species garner special protection.
   ` Can be found in the form of meats, fish, or fish roe available for
     consumption. DNA would be used to try to determine the
     number of animals involved by finding out how many unique
     DNA patterns are present.
   ` Clothing might be made from the body of a protected species.
   ` Ground into medicines - investigated by forensic chemists
* Wildlife is protected in the United States by the Department of
    Homeland Security - Border Protection Division
    Information Link
   `Protect endangered species
   `Protect our eco-systems from the introduction of invasive
    species.


Snakes in a speaker 1
Snakes in a speaker 1 (Photo credit: USFWS/Southeast)

Video Quick Study (2:14) new wildlife forensics lab to protect the wildlife
Video Quick Study (6:44) Being a Wildlife ranger - protecting the animals is incredibly dangerous. What great heroes and heroines to write into a plot line. 
Video Quick Study (6:29) CSI for wildlife

*Inspectors might find animal hair that help link a suspect to a
  crime scene (blog article: fur evidence)
* Snarge - the pulverized bird remains stuck to an airplane. 
   Samples of birds and birds pieces are kept at the Smithsonian in
   Washington D.C. The feathers and bird remains found at the
   scene or an airplane accident help to determine if the plane was
   downed by birds.
   Video Quick Study (13:22) Goes through the forensics of flight
   1549 and bird strike forensics.


The Environment - 

All of the same scene and evidence protocols have to be maintained (blog article: CSI 101)

Dead fish up close
Dead fish up close (Photo credit: severinus)
* EPA involvement
* Dead zones on land and in
   water
* Strange Odors
Dead wildlife 
* Accidental or criminal
   poisoning of the environment
   `Heavy metals
   `Insecticides
   `Gas/oil
 * Critical investigative work because these toxins enter the food
    chain and effect our health.

Video Quick Study (2:13) Dan River coal ash - human water
     supply, environmental impact.


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, March 10, 2014

Forensic Serology: Body Fluid Information for Writers


______________________________________


Soldiers of the United States Army Criminal In...
 (Photo credit: Wikipedia
At the scene of a violent crime, investigators will look for serology samples.
(CSI blog link)

Serology is simply the study of bodily fluids.

These fluids include:
* Blood
* Semen
* Saliva
* Sweat
* Tears
* Vomit
* Vaginal secretions

These fluids can be found either on the skin or transferred to another surface.


While serology tests can EXCLUDE a subject who is thought to be a person of interest, it can not find them culpable.

Serology tests are class studies and cannot tie a body fluid to a specific and unique source.
Only DNA testing can link a specific individual to a crime. (DNA blog link)



Presumptive tests - likelihood of something being what you think it is in the field.

* Sometimes a false positive - but you never want a false negative because then a detective could walk away
   from evidence and make false conclusions about the scene

Is there blood present but not visible to the naked eye?
* Fluorescein - precursor to Luminol goes back to 1900s
   `Is not thwarted by chlorine bleach
Blood Stained Floorboard Treated with Luminol
Blood Stained Floorboard Treated with Luminol (Photo credit: Jack Spades)
   ` Uses UV light to glow
   `Still used in the field today
   `Thicker than Luminol so good for
     vertical surfaces
* Luminol/BlueStar
   `Does not work if chlorine bleach
    was used to clean up the blood
   `Complicates further testing by
    diluting the blood
   `Needs darkness



When you write a scene that includes either of these tests, please remember that the blood is not visible to the naked eye because it was cleaned up. When the blood was cleaned, it was smeared around. The Luminol or Fluorecein will show up in smear streaks NOT blood spatter. NOT hand prints.

Video Quick Study (2:49) Shows luminescence of BlueStar

Is that blood? Testing for a visible stain:
At FBI doing serology tests
* Leucomalachite Green
   Video Quick Study (4:28)
* Kastle-Meyer test - phenolthaline and hydrogen
   peroxide that detects the hemoglobin in blood
   cells.
   `produces a dark pink.
   `blood can come from any animal
   Video Quick Study (1:01)

Video Quick Study (7:41) CSI teacher shows how the three presumptive blood tests are conducted.


Once the presumptive tests show that a substance is blood then the collection is sent to the lab where they undergo confirmatory tests:

1. Is it human blood?

   * The serology labs have stocks of antigens that are found in animals but not humans.
   * Samples of common animals such as: dog, cat, rabbit, deer, chicken etc. antigens  are maintained for
      testing.
   * If the test shows an antigen reacting with an antibody then that determines the species type.

2. Once it is determined that the blood is human then blood test typing is done.
   * Blood Type
Diagram of ABO blood groups and the IgM antibo...
Diagram of ABO blood groups and the IgM antibodies present in each.  (Photo credit: Wikipedia)
    `ABO system
    `Rh Protein (not used in forensic science)
    `Genetically inherited
    `Can be determined not just from
     blood but also from other body secretions.
    ` Blood type is class evidence. It is NOT
      individuating evidence. So it can only be
      used to show that someone COULD NOT
      have done the crime but cannot be used to
      prove that some did - that would require
      DNA




Video Not Quite So Quick Study (14:00) Goes over this thoroughly if it is an important point in you plot and you need a firm grasp on the importance of blood typing.




Semen

Sperm (album)
Sperm (album) (Photo credit: Wikipedia)
* Can be found in a dead woman's body for up
   to two weeks
* In a living sexual assault victim sperm can only
   be found for about five hours after the crime
   occurs
* After 72 hours in a live victim there may be no
   remaining evidence of sperm or semen
* Acid phosphatase is a presumptive field test.
   Acid Phosphate is made in the seminal
   vesicles in males but also in:
   `non-human animals
   `plants and fungi
   `found in vaginal fluids.
* Microscopic search for sperm cells in a
    sample is a confirmatory test
 * Microscopic sperm search is NOT useful if
    the man has had a vasectomy
* PSA (Prostate-specific Antigen) is considered
   confirmatory

Video Quick Study (1:01) Acid Phosphatase Test


Video Quick Study (3:15) Storage and container information for serology samples
Video Quick Study (2:31) Serologist at trial giving testimony - note the packaging of the items

Using various wave length light sources to find bodily fluids at a crime scene
All body fluids fluoresce except for blood which absorbs light
Body fluids must be dry to fluoresce except for urine (which will sometime fluoresce when wet)
Video Quick Study (2:00)


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