DNA crime-fighting tools can help crack cases, but authorities must put proper procedures in place.

by jeeg 11. July 2010 00:01


It was an unfinished slice of pizza that led to the identification of
Lonnie David Franklin Jr. as the prime suspect in the Grim Sleeper
murder investigation. But the pizza was just the final clue leading to
his arrest.

The key break in the investigation, intermittently conducted over 25
years, came when investigators found a close — but not perfect — match
between the DNA recovered at multiple crime scenes and a man being
held in a California prison. Such a near-match strongly indicated that
the person wanted by police was a close relative of the man in prison,
and police soon focused on the man's father, Lonnie Franklin. They put
him under surveillance, obtained his discarded pizza and found that
his DNA matched that recovered at a Grim Sleeper crime scene.

Four years ago, in the journal Science, we described how a data-mining
technique known as "familial searching" could be used for efficient
identification of possible crime suspects when traditional
investigative efforts fail. The paper (which we wrote along with UC
Berkeley mathematician Charles Brenner) explained how crime
laboratories might benefit from searching not just for perfect
matches, but also for close ones, when trying to connect DNA from
unsolved crimes to the DNA of known offenders whose genetic profiles
are held in local, state and national databases. Because relatives
share common DNA profiles, close matches can implicate family members
as possible crime suspects.

The importance of this technique was clearly demonstrated this week in
Los Angeles. Yet currently in the U.S., familial searching is allowed
only in California and parts of Colorado. As experience with familial
searching increases, other states will probably embrace the technique.
And as they do, it is imperative that policies be carefully crafted to
ensure both efficiency and accuracy in case selection, statistical
thresholds and follow-up testing and investigation.

Familial searching extends the size and reach of the nation's DNA
databases to effectively include the parents, children and siblings of
the 8 million offenders and arrestees whose DNA profiles are already
stored in databases. Additional technologies, including Y-chromosome
genotyping and examination of mitochondrial DNA, can provide analyses
even further out on the family tree. Extending the reach of databases
to possibly tens of millions of additional individuals brings great
opportunities for solving crimes. But it also raises concerns.

By utilizing these techniques, officials have the ability to reach far
beyond the pool of those mandated to provide DNA samples. This sparks
legitimate privacy considerations. It also magnifies concerns that
African Americans and Latinos are disproportionately represented in
offender databases, although this also can mean that the benefits of
familial searching will accrue to these overrepresented groups. This
case demonstrates that point, as Franklin and all of the Grim
Sleeper's known victims are African American.

Because of the chance that someone unconnected to a crime might appear
to be related to the perpetrator, extra laboratory testing steps are
always needed to narrow the list of potential suspects to avoid
intrusions and conserve investigative time and resources.

But California has demonstrated how these concerns can be addressed in
a way that limits the potential for intruding in the privacy of
uninvolved parties, yet allows investigators to utilize an important
crime-solving technique. The state limits familial searching to
high-priority cases when other investigative methods have failed,
requires additional Y-chromosome typing and makes use, if available,
of non-forensic information in order to identify additional evidence
bearing on relatedness.

The Grim Sleeper case will undoubtedly become the poster child case
for proponents of familial searching around the country, and indeed,
those who oppose any use of familial searching must justify not using
these methods when there is lingering ongoing danger to the public.
Still, states should put safeguards in place as California has done
before embracing the technique.

The collection of DNA by law enforcement officials has expanded over
the last decade. Initially, databases included only the DNA of those
convicted of a narrow array of violent crimes. Then it was expanded to
all convicted felons, and then, in California and many other states,
to those arrested — but not necessarily convicted — of qualifying

Familial searching is a quantum leap because it expands the potential
for DNA scrutiny to millions who have not even been suspected of a
crime. And it demands a question: If it is just the capricious hand of
fate that separates those of us under surveillance from those who are
not, what is the justification for not creating a universal database
as the only equitable solution?

Although there are many inside and outside the United States who have
made cogent arguments supporting creation of a universal database, we
would not support such an extension of state authority.

These are issues our system will grapple with over time. But in the
interim, it is essential that states tread deliberately and carefully
as they expand DNA analysis to include familial searches. Only in
doing so can our public institutions both protect our individual
rights while at the same time bring to justice dangerous criminals.

By David Lazer and Frederick R. Bieber

David Lazer is an associate professor of political science and
computer science at Northeastern University and the editor of the
book, "DNA and the Criminal Justice System." Frederick Bieber is a
medical geneticist at Brigham and Women's Hospital and an associate
professor of pathology at Harvard Medical School.




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