jimtrue.com : school : CJT2260 : 2003-09-18: Sexual Battery Evidence
Posted by Jim True on September 18, 2003 7:42 AM. Last Updated October 22, 2006 9:23 PM
Disclaimer for all material noted here is at the bottom of this web page.
Most of the crime scenes you'll be working as a crime scene technician are Burglaries, stolen vehicles, assaults, missing pets and sexual batteries. The Sexual battery is a very important case: often dealing with a very traumatized person and very fragile evidence that can be easily lost if you don't take the proper precautions.
Statistics for Rape are JUST based on the number reported; not on the actual amount of rape cases.
Know where to look (kind of trace evidence) [Cigarette butts and drinking straws] Will have to ask where the suspects mouth came into contact with the victim (what areas). Assume there is probably saliva around bitemarks.
DNA from Buccal Epithelial cells (lining of the cheeks) or Lingual Epithelial Cells (the tongue). Saliva does not have nucleal cells in it per se, it just may have epithelial cells in the matrix.
If you notice bite marks on an indivual, you can use an ALS to further enhance the bite marks, which can be used for matching dental records (Odontological comparison). Take good photographs. ALS (Alternate Light Source), saliva will not luminesce very much, you're looking for contrast on detergents on surfaces. With a dark sheet look for a whitish stain where there shouldn't be.
*Presumptive* -- Alpha Amylase, Substance in saliva to determine if they are looking at saliva or not. Alpha Amylase is produced in the salivary glands. Beta Amylase is produced in the Pancreas. Amlyase is used to break down starch.
At the lab, will have a petri dish filled with a starchy gel. Sample will be placed in the middle and given time to react. The amylase will break down the starch and iodine will be added to stain the starch. Having an clear area unstained will show there is amylase present; the amount unstained will show the amount present.
Clear spot displaying MAY have saliva present. Alpha Amylase is also present in wallpaper paste and other bodily fluids, ie breast milk.
*Serological Testing* -- Person may have secretor status; this people will exhibit there ABO type in their saliva. And more of those antigens present in their saliva than their blood.
To remove stamps or open envelopes, there is a product known as UnStick.
*Visual Exam* -- easier to spot; victim will help locate this type of evidence. Was the suspect wearing a condom, if he ejaculated, where. If there is a condom is floating in a toilet, there will probably be seminal fluid there. You will not have to submit the entire condom into the lab; a swab is sufficient.
Seminal fluid will luminesce fairly well under an ALS, UV light. Substrates will luminesce in and of themselves, light colored sheets or detergent. Potential for UV or ALS to degrade evidence. UV light will degrade DNA, no question. The dosage is dependent on the exposure.
*Presumptive* -- Acid Phosphatase (AP). Should produce a bluish purple color in the presence of AP. MAY be seminal fluid. Relatively stable enzyme. Heat and humidity are detrimental to AP. Keep your samples dry, as cold as possible without freezing them and out of direct sunlight.
*Confirmatory* -- #1 method is looking through the microscope for the little sperm cells. Stain will be applied ("Christmas Tree Stain"). This is a differential stain, meaning it will stain different parts of the sperm cells different colors. Does not confirm HUMAN sperm.
After the sperm leave the body, they will start to degrade. Parts of the sperm cell:
# Acrosome - Clear
# Anterior - pinkish
# Posterior - dark red
# Mid piece - blue
# Tail - yellowish green
What happens if No Sperm? Aspermia (disease, vasectomy)
Few Sperm? Oligospermia
Confirmatory in these examples, is a P30 test, when you cannot visualize sperm. Prostatic Antigen, produced ONLY in the prostate gland. Confirm semen present.
DNA from Semen -- Sperm Cells, not the fluid matrix (exceptions, white blood cells if the person had a bladder infections, or epithelials from the urethral lining).
*Collection* -- Pick them up with a pair of forceps, being careful not to bend or kink the hairs. Pharmaceutical fold (make sure you don't bend them).
Tape can be used; some lifting tapes are manufactured that dissolve in methanol.
Vacuum method; only vacuum the surface and be mindful of vacuuming a large area, as you will lose any indication of where the person was and where that particular trace evidence was deposited. Would have to change out filters and bags to remain specificity of location.
Will not have much probative value, if you don't have Known standards from the suspect or victim to compare it against.
Known samples will have to be collected in a particular way: different types of hairs on people (pubic, head and body hair).
Hairs on the head (regions): nape, anterior, posterior. At least 10 hairs from each region in order to get a good *representative sample*.
Just comparing morphological characteristics, the hair can be cut close to the scalp. For DNA, will have to pluck the hair to collect the root.
The area near the root with skin cells, is a follicular tag. The tag is a richer source of DNA over the root. Hair is persistent to degradation, but follicular tags are just hanging out there exposed to the elements.
Mitochondrial DNA can be gained from the shaft of the hair. mtDNA. One is like a subset of the other. mtDNA is heartier than nuclear DNA.
Hair as it pertains to sexual battery; there is a need to document to preserve and collect evidence, but you still have to be cognizant of the victim's state of mind. You can allow the victim to collect the sample themselves (good for empowering the victim).
Documentation - take a headshot for identification purposes. Subsequent shots for various injuries; keep the headshot separate from the body parts.
Bruises develop over a couple of days; better to go back 5 days later and re-take photographs of the bruises.
Disclaimer: These are MY notes taken from classroom lectures while I'm in the classroom. While I'm perfectly happy to share my notes with my classmates and I know I take very good notes, you should still make every effort to attend the class and TAKE YOUR OWN NOTES. I will not transcribe everything the instructor says in the classroom, and I will NEVER post pre-exam reviews. My notes will not replace the value of actually attending class and taking your own class notes.I also cannot attest to their accuracy, other than they are what was provided in the lecture; you should not reference my notes as "expert opionion" by any means, and if you notice an error or omission, please do me the favor of e-mailing me with the correction and I will re-post my notes. End of Disclaimer.