Docstoc

DNA

Document Sample
DNA Powered By Docstoc
					                                 Physical Evidence




\video projects\ no deals.wmv
 ...\wrongful...\earl washington.wmv
                                         DNA
...earl washington.wav
...\dna\kathleen ham.wmv
...\samantha runnion.wmv
...\what is DNA.wmv
...\dna contamined.wmv
...\larry peterson.wmv
\cold case.wmv, \cold hit.wmv
\dna\hpd crime lab.wmv
Murder of husband and mother of
Federal judge

   On Feb. 28, 2005 the husband and mother of
    Federal judge Joan Lefkow were found shot to
    death in the Lefkow’s Chicago home
   Suspicion was immediately placed on right-wing
    militants against whom Lefkow had ruled on a civil
    lawsuit. A huge investigation got under way.
   Three days later a West Allis, Wisconsin patrol officer pulled over Bart
    Ross for suspicious activities.
   Ross, an unemployed electrician and cancer victim, committed suicide.
   In Ross’s car was a note in which he confessed to the shootings. He
    was angry at Judge Lefkow for dismissing his civil lawsuit against
    medical providers.
   Ross’s DNA was matched against DNA left on a cigarette butt left
    behind in the Lefkow residence.
DNA in Girl's Tears Point
to Killer, D.A. Says AP, 3/21/2005

According to the prosecutor, DNA from
Samantha Runnion’s tears was
found in an inside door of the vehicle
used by her killer, Alejandro Avila.
More DNA material was found on
the vehicle’s center console and in
scrapings from the victim’s fingernails.
    Samantha was kidnapped in
July 2002 while playing in front of her
home with a friend. Her body was
               found the next day. She
               had been sexually
               assaulted and suffocated.
                    In an unrelated case, Avila was acquitted in 2001 of
               molesting two other girls. On 4/28/2005 Avila was convicted
               of Samantha’s murder and was sentenced to death.
Court Views Chilling Video of Serial
Killer in Action           L.A. Times 10/31/05


During a preliminary hearing LAPD showed a videotape of a
“husky muscular man forcing a woman onto the ground, raping
and strangling her.” Chester D. Turner, 38, is accused of
strangling ten women between 1987 and 1998, a period in which
he was bouncing around between prison, half-way houses and
relatives’ homes. He is suspected in as many as twenty murders,     Chester Turner
committed during a period in which L.A. averaged 1,000 homicides a year.
The trail leading to Turner began in February 1998, with the discovery of the body of
Paula Vance, 38, who was raped and strangled. In September 2003 LAPD lab
analysts extracted DNA from biological samples obtained from Vance’s body. The
DNA profile was uploaded to California’s statewide DNA database, which contains
prisoner DNA profiles. A match was made to Turner’s DNA profile. A nearby
security camera recorded the crime. Although the image is indistinct, the assailant
resembles Turner.
Additional DNA matches were later made between Turner and biological samples
from other victims. These resulted in freeing of David Allen Jones, a mentally-
retarded man who served 11 years after being convicted on two of the murders.
Thirty-two years late,
justice is served
In 1973, Kathleen Ham, 58, a
California lawyer, was raped
while living in New York city.
The trial of her alleged
assailant, Fletcher Worrell,
ended in a hung jury. Months later Worrell was
convicted in another rape and sentenced
to prison. After his release Worrell stayed in trouble with
the law and eventually left the country. He later returned.
In 2004 Worrell tried to buy a shotgun. The background
check turned up two sexual assault warrants and Worrell
was arrested. Now 59, Worrell has been linked through
DNA to 24 other rapes in New Jersey and Maryland.
First a new trial, then freedom

On July 29, 2005, the murder and
rape conviction of Larry Leroy
Peterson were thrown out after
DNA results on hairs and other
samples ruled out Peterson as
the donor. But prosecutors
remained convinced that
that Peterson was guilty
because he allegedly told several
persons that he committed the
crimes.
In 2006 prosecutors decided not to retry the case. Peterson was originally
convicted based on a microscopic hair comparison and testimony of three men
who said he confessed to them. But when these men were re-interviewed
their stories changed; one suggested he was coached by police. Prosecutors
decided to drop the case because they did not feel they had enough evidence
to convince a jury beyond a reasonable doubt.
DNA – what is it?
   Molecules that carry genetic
    information specific for each
    person
   Present in tissue, hair, bodily




                                                                         Libraryvideo.com
    secretions (e.g., sweat) and fluids
    (e.g., blood, urine, saliva)
   Arranged in two strands that
    spiral
   Each strand contains a sequence
    of “bases”, the chemicals
    Adenine, Guanine, Cytosine and
    Thymine
   Bases are bound across strands,
    but only in these “base pairs”:
      A  T           G  C

The only difference between people is in the sequence of these “base pairs”
                                                              Mom   Dad   Child
DNA analysis
   Complete DNA strands bearing a person’s full DNA
    sequence are present in the nucleus of every cell
   Full sequence of base pairs fully identifies a
    particular person. Can’t be used to make a match
    (there are too many base pairs in someone’s DNA!)
   Each person inherits repetitive sequences of 20-
    100 base pairs (VNTR, variable number tandem
    repeats). These occur at certain locations in each
    person’s DNA strands and can be matched.
   A lab typically looks at 13 places. The lab counts
    the number of repeats in each of the 13 places, and
    the overall pattern is a person's DNA profile. In fact,
    each place can yield two numbers, because people
    inherit DNA from both parents, and the number of
    repeats inherited from each parent usually differs.
   If the DNA profiles from two samples match, it's
    considered virtually certain that both samples came
    from the same person or identical twins.
Types of DNA

   Nuclear: DNA from a cell’s nucleus. It has the complete DNA sequence and
    has been accepted in Court as positive ID.
   Mitochondrial: from a cell, outside the nucleus. Present in much greater
    quantity than nuclear DNA but carries only part of the DNA sequence.
     – Cannot be used as positive ID but can rule persons out as a source
     – No general rule allowing its use in Court
     – Used in Scott Peterson trial: One hair found in his boat was linked to his
        mother-in-law (both share a DNA sequence that is present in 1 out of 112
        Caucasians).
     – Approved for use in the Samantha Runnion kidnap/murder case
   YSTR: from the “Y” chromosome, found only in males.
     – Cannot be used as positive ID
     – Useful in sex assaults when female DNA obscures other DNA sequences.
     – First application in California in the Samantha Runnion case.
Matching known to
questioned DNA

   Compare known DNA, usually an
    excellent sample taken on purpose to
    questioned DNA from a scene, often
    degraded and incomplete
   Results can be a match, elimination or
    inconclusive
      – One dissimilarity (foreign VNTR pattern) eliminates
   Probabilities can range from 1 in 20 to less than one in a million
   Errors
      – Degradation through heat, light, moisture, bacteria
      – Band shifting
      – Contamination (coughing, sneezing, skin flaking)
      – False negatives more common (one dissimilarity excludes)
      – Technical incompetence and carelessness 
Getting DNA “on the sly” --
“surreptitious sampling”

   2007 -- Buffalo, NY -- Altemio Sanchez, suspected
    serial killer, admitted killing three women, gets life
    in prison. His DNA was recovered by detectives who
    took a glass that he used in a restaurant

   2006 -- Sacramento, CA -- Rolando Gallego, who
    had passed a polygraph, was suspected in a
    murder that happened 15 years before. Officers
    followed him until he discarded a cigarette butt

   2007 -- Los Angeles -- Adolph Laudenberg,
    suspected serial killer, invited by police to
    discuss an unrelated matter, left his DNA on a
    styrofoam cup at a doughnut shop
DNA repositories

   Many States now require felons to
    submit DNA samples
   DNA typing is expensive
     –   Time-consuming
     –   Requires precision
     –   Must be careful to avoid
         contamination
   Establishing State-wide and National
    DNA databases has swamped
    laboratories and created huge
    backlogs
   BUT – repositories have led to many
    “cold hits”, mostly in sexual assaults
Using partial (familial) “hits”
to develop investigative leads

   In April 2008 Cal DOJ announced a program to search for
    partial hits in the state DNA database
   As usual, DOJ would compare “questioned” DNA recovered at
    a scene to “known” DNA profiles in the State database
     –   Normally the State only reports an exact match
     –   In this program, if there is no exact match, the State would ID any
         persons whose “known” DNA profiles are so close to the
         submitted, “questioned” DNA that they could be a blood relative
   For reasons of privacy, agencies would have to make a special
    request and provide justification before the State would release
    the identity of persons whose DNA profile was a close hit
   This procedure is used in Great Britain, but at this time
    California is the only State in the U.S. to institute the practice
Probability that a match can happen at random
(meaning, to an innocent person)

   Best match -- high a priori (before DNA) probability
     – A good “questioned” sample from the scene, with repeats present in 10 or
        more areas, AND
     – The match was made to a previously ID’d suspect’s “known” DNA
     – Probability of a random match is often very low -- 1 in 100 million or more
   Worst match -- low a priori (before DNA) probability
     – The questioned sample is degraded, with repeats present in only 7 areas
        (minimum required in California for a match), AND
     – The match to “known” DNA was produced by a database run
     – Probability of a random match depends on the prevalence of the DNA
        profile AND the size of the database
     – If the same DNA profile is present in 1 out of every 1,000,000 persons, and
        the database is contains 1,000,000 profiles (like Calif.) the probability of a
        match after the whole database is run is 1 in 1. If the population is
        38,000,000 and nothing else is known the probability of someone matched
        being guilty is 1/38.
     – Database matches most useful when questioned (recovered) DNA is so
        good that the DNA profile is shared by very few people, or when excellent
        evidence of guilt is independently developed
Virginia Governor Orders Review of
150 DNA Cases by Crime Lab NY Times, 5/7/05

An error in examining the DNA of semen found in a rape victim, which
nearly led to the execution of the wrong person, led Virginia’s governor to
order a complete review of all cases handled by the lab’s director,
Jerry Ban. The lab twice failed to identify the donor of the semen found in       Earl Washington, Jr.
a victim even though he was a known, convicted serial rapist. With the DNA        Innocent but nearly
                                                                                        executed
unidentified, there was nothing to keep Washington from taking the blame.
Auditors from the American Society of Crime Laboratory Directors sharply criticized the
Virginia lab, once thought to be the nation’s finest, for caving in to pressures from the State’s
former Governor to quickly solve cases.
Houston PD
crime lab scandal

   Major report in June 2007 cited poor
    procedures and poorly trained personnel
   The lab’s work was called seriously deficient
    across the board, casting doubt on
    thousands of convictions
   Poor analyses were found of firearms
    evidence, controlled substances, DNA and serology, the science of typing body
    fluids.
   The panel called for a review of 180 cases in which serology was used to
    determine whether the lab’s findings played major role in securing convictions.
    So far, serology and DNA errors led to three known wrongful convictions:
      – Ronald Taylor - failed to find the real perpetrator’s DNA on victim’s bed
         sheet
      – Josiah Sutton, exonerated and released from prison in March 2003 when
         DNA tests challenged the HPD work on a 1998 rape.
      – George Rodriguez, served more than 17 years in prison in the 1987 rape
         of a 14-year-old girl before new evidence discredited the HPD findings

Investigative panel website             Full report      Summary

				
DOCUMENT INFO