Why is semen important in an investigation? Evidence in sexual assault cases Can prove crime was committed Can identify perpetrator

What is semen? cells, amino acids, sugars, salts, ions and other organic and inorganic material

 Also called spermatozoan  Approx 55 μ m in length  Head contains cell nucleus which packed with DNA

Presumptive test Test for SAP (seminal acid phosphatase)  Look for color change  Brentamine Fast Blue Test get intense purple color within 2 minutes

 Microscopic examination  Motility usually not apparent by time lab gets stain  Use staining techniques

 Commonly used staining techniques  Picroindigocarmine (PIC)  Nuclear Fast Red (aka Christmas tree stain)

 Need to determine best use of sample  Only single intact sperm cell needed to ID sperm  however, 80 sperm cells required for DNA profile

 Time since intercourse  If clothing has been washed  SAP is water soluble  SAP can be detected after dry cleaning

 Sexual assault kits utilized to collect evidence – “rape kits”  Swabs examined first  Liquid samples examined next

 Contains water, mucus, proteins, salts and enzymes  Human produce liters per day

 No test specific for saliva  Basically looking at amylase  Problems with amylase, also found:  Pancreas, perspiration, vaginal secretions, and semen

 Cases of harassment, mischief, sexual assault, etc.  Stains identified through visual examination (alternate light may help)  Rarely used; difficult to identify as urine and difficult to get DNA profile Searching for Urine

Feces end product after digestion Undigested food, mucosal cells, bacteria Identified by greenish brown color, odor, undigested food

 Low cell count and high bacteria content make testing difficult, but not impossible DNA testing of Feces

 DNA testing unsuccessful due to inhibitory effects of bile pigments

 No known test Possibly look at low pH, or undigested food

 Determine if body fluid is present  Record findings  Determine necessity of further testing  Determine type of further testing

 Assess type and whether victim alive  Awareness of victim  Number of people involved  Relationship of principals  Time elapsed  Actions after event