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دانشكده پزشكی تهران , daneshkade_pezeshki

دانشكده پزشكی تهران

دانشكده پزشكی تهران , daneshkade_pezeshki

دانشكده پزشكی تهران

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دانشكده پزشكی تهران , daneshkade_pezeshki
Using DNA to Solve Cold Cases
Introduction

In 1990, a series of brutal attacks on elderly
victims occurred in Goldsboro, North
Carolina, by an unknown individual dubbed
the “Night Stalker.” During one such
attack in March, an elderly woman was
brutally raped and almost murdered. Her
daughter’s early arrival home was the only
thing that saved the woman’s life. The
suspect fled, leaving behind materials
intended to burn the residence and the
victim in an attempt to conceal the crime.
In July 1990, another elderly woman was
brutally raped and murdered in her home.
Three months later, a third elderly woman
was raped and stabbed to death. Her husband
was also murdered. Their house
was burned in an attempt to cover up the
crime, but fire/rescue personnel pulled
the bodies from the house before it was
engulfed in flames.
When DNA analysis was conducted on
biological evidence collected from vaginal
swabs from each victim, authorities concluded
that the same perpetrator had
committed all three crimes. However,
there was no suspect.
For 10 years, both the Goldsboro Police
Department and the crime laboratory
refused to forget about these cases. With
funding from the National Institute of
Justice, the crime laboratory retested the
biological evidence in all three cases with
newer DNA technology and entered the
DNA profiles into North Carolina’s DNA
database. This would allow the DNA profile
developed from the crime scene evidence
to be compared to thousands of
convicted offender profiles already in the
database.
In April 2001, a “cold hit” was made to
the perpetrator’s convicted offender DNA
profile in the database. The perpetrator
had been convicted of shooting into an
occupied dwelling, an offense that
requires inclusion in the North Carolina
DNA database. The suspect was brought
into custody for questioning and was
served with a search warrant to obtain a
sample of his blood. That sample was analyzed
and compared to the crime scene
evidence, thereby confirming the DNA
database match. When confronted with
the DNA evidence, the suspect confessed
to all three crimes.
Mark Nelson, special agent in charge of
the North Carolina State Crime Laboratory,
said, “Even though these terrible crimes
occurred more than 10 years ago, we
never gave up hope of solving them one
day.”
Every law enforcement department
throughout the country has unsolved
cases that could be solved through recent
advancements in DNA technology. Today,
investigators who understand which evidence
may yield a DNA profile can identify
a suspect in ways previously seen only on
television. Evidence invisible to the naked
eye can be the key to solving a residential
burglary, sexual assault, or murder. The
saliva on the stamp of a stalker’s threatening
letter, the perspiration on a rapist’s
mask, or the skin cells shed on the ligature
of a strangled child may hold the key
to solving a crime.
In Austin, Texas, for example, an investigator
knowledgeable about DNA technology
was able to solve the rape of a local
college student. Having read about the
potential for obtaining DNA evidence from
the ligature used to strangle a victim, the
investigator requested DNA testing on the
phone cord used to choke the victim in his
case. He realized that in the course of
1
Introduction
2
SPECIAL REPORT / JULY 02
choking someone, enough force and friction
is applied to the rope or cord that the
perpetrator’s skins cells may rub off his
hands and be left on the ligature.
The investigator’s request paid off in an
unanticipated way. In spite of the attacker’s
attempt to avoid identification through
DNA evidence by wearing both a condom
and rubber gloves, a reliable DNA profile
was developed from the evidence. During
the struggle, the attacker was forced to
use one hand to hold the victim down,
leaving only one hand to pull the phone
cord tight. The attacker had to grab the
remaining end of the cord with his mouth,
thereby depositing his saliva on the cord.
Although the developed profile came from
saliva rather than skin, DNA not only
solved the case in Austin, but also linked
the perpetrator to a similar sexual assault
in Waco.
Without the investigator’s understanding
of DNA technology and where DNA might
be found, the case may have gone
unsolved. The successful review and
investigation of unsolved cases require
the same basic elements as the investigation
of new cases: cooperation among law
enforcement, the crime laboratory, and
the prosecutor’s office. Investigators
should be aware of technological
advances in DNA testing that may yield
profiles where previous testing was not
performed or was unsuccessful. The
crime laboratory can be essential to the
preliminary review of unsolved cases, for
example, by providing investigators with
laboratory reports from previous testing
and consultation regarding the investigative
value of new DNA analysis techniques
and DNA database search capabilities.
Additionally, the prosecutor’s office should
be involved as soon as a case is reopened
so that legal issues are addressed appropriately.
It is also extremely important that
case reconstruction considers the victim
or victim’s family and the importance of
finality to closing a case.
Although DNA is not the only forensic tool
available for the investigation of unsolved
cases, advancements in DNA testing and
the success of DNA database systems
have inspired law enforcement agencies
throughout the country to reevaluate
cases previously thought unsolvable. The
purpose of this report is to provide law
enforcement with a practical resource for
the review of old, cold, or unsolved cases
that may be solved through DNA technology
and DNA databases. “The Long and
Short of DNA” and “How Can DNA
Databases Aid Investigations?” will educate
the reader about the science and
technology of DNA testing and DNA databases.
“Practical Considerations” provides
important background information on legal
and practical considerations regarding the
application of DNA technology to old, cold,
or unsolved cases. Finally, a step-by-step
process is provided to help investigators
select cases that would most likely be
solved with DNA evidence. As investigators
advance through this process, they
should also keep in mind the array of
other technology advancements, such as
improved ballistics and fingerprint databases,
that may benefit their investigation.
ادامه
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