Forensic Biology

Origin of Forensic Biology

• Used to be called Forensic Serology

  • Serological techniques to determine possible origin of fluid/stains

Modern Day Forensic Biology

Chemical tests, molecular biology, population genetics, statistics, and computer algorithms, crime scene reconstruction, and bloodstain spatter

Major Crimes

• Homicide

• Assault

• Sexual Assault

• Burglary/Robbery

Homicide

Conduct that causes the death of a person/unborn child (24 weeks+): manslaughter, murder, abortion, self-abortion, or criminally negligent homicide

Abortion

Someone other than pregnant woman terminates a baby 24+ weeks

Self-abortion

Pregnant woman herself terminates pregnancy of 24+ weeks

Homicide Charges

Murder, manslaughter, criminally negligent homicide

Murder

• Intent to cause death of another, and does cause death

  • 1st or 2nd degree

1st Degree Murder

Intending to kill someone with premeditation

2nd Degree Murder

Intending to kill someone without premeditation (in the moment)

1st degree Manslaughter

Intending to cause serious physical harm, but instead causes their death

WANTED to cause injury, caused death instead

2nd degree manslaughter

Recklessly causing the death of another, without intent to harm them

Manslaughter vs. Negligence

In negligence, you are unaware of the risks but in manslaughter, you are but do it anyways

Criminal Negligence

Person acts without being aware of the risks, although they should

They have deviated from standard of care a reasonable person would take

Examples of criminal negligence

Leaving a child in hot car, medical professionals, etc.

Rape

Penetration of the vagina or anus with any body part/object or oral penetration without consent (force/deception/etc)

Statutory Rape

Victim is below the age of consent, perpetrator is above age of consent

Sodomy

Anal or oral copulation without consent

Majority of Rape Victims are..

Female

Reasons sexual assault isn’t reported:

Personal, fear of reprisal, police bias

If victim knows the perpetrator

Element of EVERY sex offense

Lack of consent

Lack of consent can result from:

• Forcible compulsion (harm, weapon, etc.)

• Incapacitated (drunk, disabled, child)

• Did not consent (no)

Treating Minors

• Minors who can give informed consent, can get treatment for sexual assault

• Cannot be forced to undergo exam

• Must be confidential

People incapable of consent:

• Minors (<17)

• Mentally incapacitated

• Intellectual/physical disability

• Committed to prison/hospital where assailant is an employee

All patients reported sexual assault…

MUST be examined (regardless of length of time)

SANE Nurse

Specialized nurses in treating sexual assault victims and collecting evidence

Sexual Offense Evidence Collection Kit

Used to collect and preserve evidence of sexual assault

Chain of Custody of Sexual Assault Kits

• ONLY sealed kits

• Each item labeled (name/patient/date/description/source)

• Reseal with Tamper Evident Tape

Forensic Photography

• Photos taken when evidence is short-lived

  • Create permanent record

• Injury should be visible

Photographing Bite Marks

Use scales and special lighting

Bite Mark Evidence

1. Photograph before swabbing

2. Collect swabs with de-ionized water

3. Put in dried secretions box

Drug-facilitated Sexual Assault

• Specimens collected ASAP

• Urine and blood testing for GHB/Rohypnol

Sexual Assault Kit Items

• Oral, anal, vaginal, buccal, cervical swabs

• Trace evidence

• Underwear

• Debris

• Dry secretions

• Fingernail scrapings

• Head, pubic hair pulls

• Pubic hair combing

Trace evidence

Clothing should be collected over a paper on the floor to collect trace evidence that falls off

Collecting Clothing

• Collect all clothing during/after assault

• Individually packaged

• No plastic

• Allow wet stains to dry

• Do not cut tears/holes

Fingernail Scrapings

Scrape under each nail over paper towel, separate for each hand

Pubic Hair Combings

Collected over paper towel under pubic area, fold up

Pulled Hair Strands

Collect without causing trauma, if needed at a later date

Swabbing

Should use 2 swabs for each area (8 total)

Matted hair

• Should examine head and pubic area for matting

• Cut off matted hair in debris collection envelope

Hospital Responsibility

Maintain a rape kit until the victim confirms they want police involvement (kept for up to 20 years)

Documenting Evidence

• Important first step

  • Needed to refresh analyst’s memory

• Condition of packaging and evidence

• Stains

• Test results

Collecting Samples

• Assume DNA typing will be done (keep sterile)

• Gloves, 5-10% bleach with flame for forceps

• Photo before removing stain

• Clothing diagram

Biological Stains

• Blood

• Semen

• Saliva

• Urine

• Feces

Blood Components

• RBCs, WBCs

• Platelets

• Plasma = liquid portion

Presumptive Blood Tests

• Appearance (color, fluorescence)

  • Blood does NOT fluoresce

• Phenolphthalein

• Leuoc-Malachite Green

• Luminol

Luminol

• 3-Aminophthalhydrazede

• Detect microscopic amounts of blood (that was cleaned)

  • Emits light (must be in dark)

• Cross-reacts with cleaning agents and metals

Species ID tests

Antiserum and DNA-based

Antiserum Based Test

Uses species-specific antisera that precipitates when mixed with antigen (CLOTS)

Ring Precipitin Test

Unknown eluate of bloodstain is layered over known antiserum, allowed to stand and examined for white ring (KNOWN = UNKNOWN if ring)

Semen

Thick, whitish secretion of male reproductive organ containing spermatozoa

Male organs that produce sperm

Prostate, seminal vesicles, Cowper’s gland, glands of Littre

Semen ID Tests

• Acid-phosphatase test (ACP)

• Microscopy

• Prostate Specific Antigen (PSA)

Visual Appearance of Semen

• Dried = crusty stain

• White to yellow

• Monochromatic light can help visualize (Crimescope)

Crimescope

UV/Vis and Infrared light that helps detect semen/sperm

Acid Phosphatase Test

• Relies of liberation of napthol by phosphatase, coupling with blue B to form purple azo dye

• Can’t determine postcoital intervals

Purple Acid Phosphatase Test means…

Semen is present

Confirmation of Semen Tests

• Sperm search and PSA

  • Prepared on glass slide

  • Stained with nuclear fast red

Red PSA test means…

Spermantigen present

Green PSA test means…

Vaginal cells present

PSA (prostate specific antigen)

• Single chain glycoprotein

• Significant in prostate tissues/secretions/semen

Seratec PSA Test

• Sandwich immunoassay with monoclonal mouse anti-PSA antibody

• Binds PSA in sample, to second antibody forming red line = POSITIVE

Saliva

• Identified based on the concentration of amylase

  • Hydrolyzes starch

• Fluoresce under light

• Sandwich antibody assay to test

Feces

• Identified mainly based on appearance (color/odor)

• Fecal stain confirmed by microscope

Edelman’s Test

Detects urobilinogen in fecal material (breakdown of hemoglobin)

Urine Identification

• Presence of urea and

• Weakly fluoresces

• Discoloring of fabric depending on background color of material

• Odor due to ammonia

Urea

Major end product of protein metabolism found in urine

Creatinine

Major excretory product in urine

RSID

Urine test that finds Tamm-Horsfall protein

Tamm-Horsfall Protein

Most abundant protein in urine, secrete by Loop of Henle