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

DNA Structure

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)

DNA Extraction

• Organic extraction

• Differential lysis

• Polymer beads

VNTRs

RFLP Profiling

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

Polymerase Chain Reaction (PCR)

Short Tandem Repeats (STRs)

CODIS STR Loci

PCR Kits

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

TWGs and SWGs

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

Mitochondria

Mitochondrial DNA (mtDNA)

Mitochondrial DNA

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

Y Chromosome STRs

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 Big Myth

• DNA match = guilt

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

Questions?