It Came From the Genetics Lab:
DNA, the Monster That Ate Forensic
Science
Walter Rowe
Department of Forensic Sciences
The George Washington University
Before DNA
• Fingerprints and dental records were the only reliable methods of personal identification
• Forensic serologists could type some genetic markers in dried biological stains– ABO blood type
– Rh types
– Polymorphic proteins (e.g. PGM, Hb)
• Microscopical hair comparisons were accepted routinely by courts
• The identification sciences (fingerprints, document examination, firearms and tool mark identification) were not challenged in court
Before DNA
• The was little inter-laboratory standardization for forensic laboratories
• Few forensic laboratories did proficiency testing on a continuing basis
• Forensic laboratory accreditation through the American Society of Crime Laboratory Directors was voluntary
• There was no CSI effect
1983
• Alec Jeffreys discovers variable number tandem repeats (VNTRs) and develops multi-locus restriction fragment length polymorphism (RFLP) probes
• Kary Mullis develops polymerase chain reaction (PCR)
RFLP Led to….
• The Technical Working
Group for DNA Analysis
Methods (TWGDAM)
• DNA Identification Act of
1994
– Establishment of the
Combined DNA Index
System (CODIS)
– DNA Advisory Board (DAB)
• CODIS became fully
operational in 1998
We Object!
• Novel science
• Lack of standards
• Statistics
– Data bases
– Error rate
– Product rule
– Race
• Privacy
Impact of DNA on Criminal Investigations
• ‘Cold’ hits– Unsub sexual
assault cases
• Cold cases
• Familial DNA
• Post-conviction DNA testing
A Local Cold Case
• May 1988 Veronica
‘Tina’ Jefferson raped
and fatally shot in
Arlington
• December 1988 Rachel
Raver and Warren
Fulton abducted in DC
and murdered in Reston
A Local Cold Case
• 2000 DNA testing linked the Jefferson and Raver/Fulton cases
• 2005 DNA profiles in Virginia cases re-submitted to CODIS
• CODIS gave hits to Alfred Prieto’s DNA
• 2008 Prieto was convicted in Virginia and condemned to death
• 2010 Prieto’s DNA linked to two unsolved murders in Riverside, California
Post-Conviction DNA Testing
• In 1985 Kirk Bloodsworth was convicted of the rape and murder of a 9-year-old girl in Rosedale, Maryland
• In 1993 DNA testing of the semen on the victim’s underwear excluded him
• In 2003 DNA testing identified the actual murderer as Kimberly Shay Ruffner
• In 2000 the Innocence Protection Act established the Kirk Bloodsworth Post-Conviction DNA Testing Program
Impact of DNA on Forensic
Laboratories
• Standardization
• Documentation
• Proficiency testing
• Cleanliness
• Mandated
accreditation
More Collateral Damage
• DNA profiling destroyed microscopical hair comparisons
• Attacks on DNA profiling became template for attacks on identification sciences (fingerprints, document examination, firearms and tool mark identification)
• 2009 NRC issued report on the status of forensic science
Mitochondrial DNA
• Mitochondrial DNA (mtDNA) is maternally
inherited
• Unlike nuclear DNA, mtDNA is multi-copy
• Forensic samples on which mtDNA sequencing
may be used:
– Bone
– Teeth
– Hair
Why There Is No Vietnam Unknown
Service Member
• In 1984 partial skeletal remains of a supposedly unknown American service member were interred in Arlington National Cemetery
• In 1994 a POW/MIA activist claimed that the remains were those of 1LT Michael Joseph Blassie
Why There Is No Vietnam Unknown
Service Member• In 1998 mtDNA
sequencing confirmed the remains were those of Blassie
• Blassie was shot down near An Loc in 1972
• All active duty military personnel must submit blood samples to the Armed Forces Repository of Specimen Samples for the Identification of Remains (AFRSSIR)
New Vistas
• Y chromosome STRs
• ‘Touch DNA’
• Microbial DNA– Biological warfare agents
– Human microbiome
• Phenotype-informative SNPs
• Ancestry-informative SNPs
• DNA labs on chipsSNP = single nucleotide
polymorphism
Another Cold Case• 1991 Sarah Yarborough
murdered on her high
school campus in
Seattle.
• 2010 Perpetrator DNA
linked to the family of
Robert Fuller who
arrived in
Massachusetts in 1630.
• Y STR profile was
submitted to a
genealogy database.
The Jane
Mixer Case
• In 1969 Jane Mixer
was found strangled
and shot to death
• Her murder was
attributed to the
Michigan Coed
Murderer
• In 1970 John
Norman Collins was
convicted of one of
the Michigan Coed
Murders
Another DNA Triumph
• In 2002 DNA tests were conducted on Mixer’s panty hose and a spot of blood scraped from Mixer’s left hand
• Mixer’s DNA was not detected on her panty hose
• DNA on the panty hose from saliva, sweat or skin cells was matched to Gary Leiterman
• Leiterman was convicted in 2005 of Mixer’s murder
Another DNA Triumph
• DNA from the spot of blood matched convicted killer John Ruelas
• In 1969 Ruelas was 4 years old and lived 40 miles from the murder scene
• Evidence from Ruelas’scase was processed in the DNA lab about the same time as the evidence in the Mixer case
What Could Go Wrong?
• Mislabeling of
samples
• Cross-contamination
of samples
• Fabrication of
evidence