How San Diego County's forensic scientists and field personnel are
teaming up to solve cold cases, identify serial killers and rapists,
and free the innocent
Commentary by Greg Thompson and Emily Williams, San Diego Union-Tribune
At twilight, as the workday ends for most San Diegans, Sheriff's
deputies at the Lemon Grove station gather for roll call. It's the
night shift and over the next 12 hours these patrol deputies will
respond to every manner of call, reflecting the everyday woes of
urban life: domestic violence and child abuse, burglaries and auto
thefts, and murder. They're well trained. The laws of arrest and
search, the rules of high speed pursuit, the skills of take-down,
apprehension, and use of force - these are second nature because of
hours of instruction.
DNA in the courtroom
Taking DNA from the crime scene to the court roomBut on this summer
evening their roll call training is different. It doesn't come from a
street-wise sergeant, but from a young woman, a scientist - a
criminalist at the San Diego Sheriff's Crime Laboratory. Her topic:
the proper collection and preservation of biological evidence.
It's a scene that will strike some as incongruous, but one that plays
over and over throughout San Diego County, a freeze-frame of historic
change. Never before have the tools of science played such a critical
role in crime detection and criminal justice.
The power of forensic science has been popularized and mythologized
by prime-time television. "CSI" and its progeny draw huge audiences
as crime scene investigators solve brutal crimes with slick, seamless
effectiveness. Real life is messier - at least in part because real
crime scenes are messy. When criminalists and field evidence
technicians, who comprise the sheriff's CSI Team, roll to the
aftermath of a homicide, the scene they confront is often chaos:
blood, hair, fibers, all manner of things which may be clues to
solving the crime - or may not.
The job of forensic science - and the professionals who've committed
themselves to this work - is to cull order out of the chaos. And the
devil, as the saying goes, is in the details.
The young criminalist conducting the training session holds out a
field kit for collecting biological evidence, opens envelopes of
sterile swabs, demonstrates how to collect a stain of blood from a
piece of glass from the scene of a burglary. She reminds the deputies
of the methods to reduce the risk of contamination, instructs them on
the collection of a reference swab - how to swipe the swab inside the
mouth of a suspect or victim in order for it to be compared against
the unknown sample. There are practical exercises for the deputies,
to try out what they've learned.
The deputies are smart, attentive, want to get it right; indeed, they
need to get it right.
Consider this case. Sheriff's patrol deputies and detectives linked a
car to the bloody killing of a young man, seized the car and with
careful precision preserved it as a "crime scene." As a result,
criminalists were able to extract DNA from the steering wheel of the
car and more DNA from the hammer of a recovered gun. Firearms experts
at the laboratory then matched shell casings to the gun, thereby
identifying the murder weapon and the DNA of the person who used it.
What was missing was a name, the suspect himself. Who was he?
Lab fingerprint examiners lifted a fingerprint from the interior of
the car and were able to identify a person from San Diego's
fingerprint database. It was then a matter of determining whether
that person's DNA matched what was found on the steering wheel and on
the gun. It did.
In this fashion, crime laboratory forensic professionals, each with
unique expertise, came together to help point detectives and
prosecutors to the killer. It was as if he were surrounded by
forensic evidence demanding his surrender.
In the new world of forensic science, the training of front-line law
enforcement becomes a new priority, the quality of the evidence being
only as good as the skill of those who identify it and collect it.
Sheriff's detectives long ago earned a reputation for being on top of
their game in this arena and now the department has committed itself
to creating an unbroken chain of expertise: from the deputy on the
street to the investigator on the case through the forensic
laboratory and into the courtroom.
Still, the sheer capacity of forensic science today creates another
kind of challenge: it creates case backlogs. Recently, a witness
testifying before a congressional committee opined that there were as
many as a half million "rape kits" stored by police and unexamined
for their evidentiary value. Inquiring minds might ask how such a
backlog came to be.
The answer comes in understanding the advances in technology and
forensic science. Just a few short years ago, DNA profiling was
limited by the amount of DNA that could be physically extracted from
a stain. When PCR (polymerase chain reaction) developed, the amount
and quality of DNA required to obtain a profile were dramatically
reduced. That cleared the way for creating a nationwide database of
standardized DNA profiles. As a result, crimes are being solved,
sexual predators arrested - some many years after their crime. What
was a cold, dead file now takes on life - and in effect creates a
backlog of unsolved cases against dangerous offenders.
The syllogism is simple: New science creates new opportunity to
analyze old evidence, which in turn creates a higher demand for the
scientific examination of evidence.
In San Diego, the sheriff's laboratory and San Diego police
laboratory have worked with police agencies countywide, solving cold
cases and delivering some of the best results in the nation. None of
this is cheap. Staffing a forensic laboratory with first-rate
professionals and equipping it with cutting-edge equipment are
Even so, there's a human cost for failing to do so.
By the time homicide detectives arrested Clyde Wilkerson last year,
he had left his mark as a serial killer, his target of preference
being women of any age. For years he eluded capture until a
criminalist in the sheriff's laboratory, working with the detectives,
linked his crimes together - and him to the crimes. He's now doing
life in prison.
Part of staying current in forensic science is anticipating the
future. There will come a day when the sheriff's CSI Team rolls to
the scene of a homicide, and analyzes drops of blood with a small
hand-held device, and in short order learns the sex, hair and eye
color, and ethnic origin of the blood's donor. A check of a DNA
databank may reveal his name.
For now, forensic science will continue to unravel mysteries of crime
that were once thought unsolvable at a pace that will seem far too
In a tragic case, a young woman, living in Northern California, was
sexually assaulted in her home. Helena Greenwood and her husband then
moved to Del Mar, in part to escape the memory of her ordeal. She was
scheduled to return north to testify at trial but she never made it;
she was strangled to death outside the courtyard of her home.
Detectives suspected that Paul Frediani, the man who had sexually
attacked her, had killed her to silence her. But they couldn't prove
it and 15 years elapsed, the case unsolved.
Then came a breakthrough.
A detective working the cold case asked that fingernail clippings
taken by a sheriff's crime scene investigator at the victim's autopsy
be examined for DNA evidence. The analysis showed that in Helena
Greenwood's desperate, futile struggle for life, she had scratched
her attacker; Frediani's DNA was under her fingernails.
This dramatic turnabout prompted one commentator, who followed the
case, to conclude that forensic evidence is about "the speech of the
dead. About how the breathless can still whisper, and science can
amplify their whispering until they are given back the clarity denied
them in life."
Indeed, the voice of forensic science is being heard throughout San
Diego as street cops, investigators, and crime lab professionals find
new ways to team up against crime and protect the public.