Forensic Biology Screening Workshop

Case Studies

Case Studies

• Blood case – homicide

• Sex Assault – juvenile

• Burglary

Case Study #1• Scenario:

– 37 year old male victim found dead in home– Victim found in bedroom– Victim was stabbed– Broken window = POE– No evidence of sex crime

Case Study #1

• Evidence sent in for analysis:– Knife from outside back door– Swab of red brown stain at POE– Fingernail scrapings from victim– Victim’s clothing– Swabs from red brown staining throughout

house

WHAT QUESTIONS WOULD YOU HAVE FOR THE DETECTIVE ON THE CASE PRIOR TO WORKING ON EVIDENCE?

Case Study #1

• What is the best evidence?

• How would you screen:

– Fingernail scrapings– Knife– Swab from broken window– Victim’s shirt

Case Study #1

• What might be the problem with screening victim’s clothes?

• Suspect may or may not be bleeding

• Victim was stabbed – a lot of victim blood and possible little suspect blood

Case Study #1

• Stain selection is KEY when you have numerous POSITIVE areas to send on for DNA testing

• EXAMPLE:– Case Study #1– Victim shirt– Several stains– On the back side wearing there are several

stains…

Case Study #1

Which stain has best chance of being from the suspect?

Case Study #1• Results:

– Shirt = KM POS

– Knife = KM POS

– Swab from window = KM NEG

– Fingernail scrapings = Swabbed for DNA

Case Study #1

• How would you report your results?

– Shirt

– Knife

– Swab from outside window

– Fingernail scrapings

Case Study #2• Scenario:

• 5 year old girl complains of possible sexual assault by male babysitter

• Parent’s bring her to hospital within 3 hours of possible attack

QUESTIONS FOR DETECTIVE?

Case Study #2• Upon further information from the detective

– Vaginal penetration, unknown if penis or digital

– Breasts were touched and possibly licked

Case Study #2• Evidence collected:

– Vaginal swabs– Breast swabs– Oral swabs– Panties– Shirt– Pants

WHAT WOULD YOU TEST FIRST?

Case Study #2

• How would you screen?

– Vaginal swabs– Breast swabs– Oral swabs– Panties– Shirt– Pants

Case Study #2• RESULTS:

– Vaginal swabs AP= NEG, MICRO=NEG, AMYLASE=POS

– Breast swabs AMYLASE = NEG

– Oral swabs AP = NEG, MICRO= NEG

Case Study #2

– Panties AP = NEG, AMYLASE = INCONCLUSIVE

– Shirt AP = NEG

– Pants AP = POS, MICRO = NEG, P30 = POS

Case Study #2• How would you report your results?

– Vag swabs– Breast swabs– Oral swabs– Panties– Shirt– Pants

Case Study #3• Scenario:

– A jewelry store was broken into– Glass door broken = POE– Clerk was hit with butt of gun

Remembers suspect wearing gloves, ski mask, baseball cap

Case Study #3• Evidence collected for analysis:

– 1 white cotton glove– Black ski mask– Baseball cap– Swab of r/b stain at POE

QUESTIONS FOR THE DETECTIVE?

Case Study #3• What tests would you perform on:

– Glove

– Ski mask

– Baseball cap

– Swab

Case Study #3• How would you report your results?

– Glove

– Ski mask

– Baseball cap

– Swab