Effective Use of Scientific Evidence: Lessons From the Simpson Trial
by: Edward G. Bernstine, Ph.D., Harold J. Bursztajn, M.D. and Joanne Wilkens,
M.A.*
* Dr. Edward G. Bernstine, a geneticist and molecular biologist, provides
consulting services to attorneys on the preparation of scientific matters.
He and Dr. Bursztajn collaborate on projects involving the communication
of scientific evidence to judges and juries. Dr. Harold J. Bursztajn,
Associate Clinical Professor and Co-Director, Program in Psychiatry and
the Law, Harvard Medical School at the Massachusetts Mental Health Center,
practices both as a clinician and as a forensic psychiatrist consulting
locally and nationally to attorneys and institutions. Joanne Wilkens,
M.A., is a corporate communications executive and a writer.
Introduction
Scientific thought and analysis pervade the practice of law. Attorneys
must understand deep technical arguments, work with experts to communicate
scientific matters to judge and jury, and advocate positions in closing
arguments. The Simpson matter offers a worthy study of physical evidence
as the product of human endeavor, its presentation to jury and the role
of scientific evidence in jury decision making. The case demonstrates
that effective use of expert testimony involves more than simply presenting
an expert's credentials. The principles that emerge from a study of Ca.
v. Simpson are of value to all attorneys who use scientific evidence,
whether in civil or criminal proceedings. In this article, we formulate
guidelines for the effective communication of technical material to judges
and juries. In a subsequent paper, we will examine the role of emotion
in a jury's ability to digest, integrate and use scientific evidence.
Science and the Law
In both civil and criminal cases, the justice system determines what happened
and who was responsible for it. Scientific evidence often plays a key
role in these determinations, a role likely to increase as scientists
develop more advanced analytical methods. Table 1 presents some of the
areas of scientific inquiry that regularly appear in legal practice.
Table 1
Areas of Science Commonly Used in Legal Practice.
Physical sciences |
Chemistry |
Biomedical sciences |
Behavioral sciences |
Engineering
Material sciences
Ballistics, tool marks
and impressions
|
Environmental
sciences
Drug screening
Alcohol testing
Narcotics testing
Fires and explosions
|
Forensic psychiatry and other medical specialties
Biochemistry
Pathology
Toxicology
Pharmacology
Physiology
Serology
Genetics/molecular biology
|
Psychology
Sociology |
In criminal law, behavioral sciences address the mens rea issues. In civil
law, physical and behavioral science provide evidence concerning liability
and negligence and assess harm borne by a plaintiff or a plaintiff's
property. Behavioral science plays a major role in discrimination and
harassment cases by determining whether the evidence shows the "reasonable
person" criterion has been met and by applying a variety of psychological
tests to determine the state of mind of the parties.
In criminal law, physical evidence collected from a crime scene frequently
forms an important element of both prosecution and defense cases. In
such cases, verdicts depend on a jury's understanding of scientific evidence.
One of the newest and, thanks to the Simpson case, most familiar methods
in use is forensic DNA testing, which is used in both civil and criminal
matters. This breakthrough technology has already resulted in the successful
prosecution of many cases of rape that might otherwise have been impossible
to prove. In addition, DNA analysis proves the innocence of Rout one
third of suspects who undergo testing. Exculpatory DNA evidence is conclusive
- failure to match excludes a suspect completely.
Demands of DNA
\
DNA technology is useful in law only if attorneys and their expert witnesses
impart the meaning of DNA evidence to a jury. To comprehend how forensic
DNA testing actually works requires significant knowledge of biochemistry
and genetics. Thus, in presenting a DNA case, an attorney must understand
the risks of exposing a jury to confusing monologues on basic science,
however interesting that science may be to specialists. In addition,
procedures employed in DNA testing laboratories consist of a large number
of steps each of which is impossible to understand without detailed explanation.
Providing such explanations can confuse a jury and diminish the impact
of the evidence. Fortunately, the results of DNA analysis are readily
understood if properly explained. Effective lawyering therefore emphasizes
DNA results.
Incriminating DNA evidence is circumstantial, but DNA results can nonetheless
be strongly incriminating. A "match" between a defendant's
DNA and DNA from a crime scene allows statements such as: "the DNA
type found in specimens at this crime scene matches this defendant's
type, and only one person in a billion randomly chosen people would be
expected to have this type." This "random match probability" is
the only form of positive conclusion supported by a match between a
forensic sample and a "reference" sample derived from a known
person. Thus, DNA evidence permits only a statement of probability. The
results never prove that a particular DNA specimen was contributed by
a specific person. Prosecutors must present such abstruse statistical
reasoning to juries with extraordinary care in order to retain the impact
of the evidence. Defense attorneys should hold the prosecution to statements
bounded by the statistical limitations of the technology. specifically,
defense counsel should prevent any suggestion that the probability calculated
from a DNA result represents the odds that the forensic sample originated
from a person other than the defendant.
In spite of its potential to provide powerful evidence, there is always
a chance, even if it is one in a billion, that a match could falsely
implicate the defendant. Therefore, the tolerance for additional uncertainty
in a DNA case is extremely narrow: the DNA evidence itself must be beyond
reproach, particularly if it is the only evidence. Procedures and policies
used by police, criminalists and forensic scientists should be scrutinized
by both prosecutors and defense attorneys to assure that the DNA results
have been obtained under stringent conditions.
Experts Represent the Evidence
What it's really about is whether the jury trusts the messenger,
and the messenger is everybody [in] that courtroom on the other side
- the police, the prosecution, the people who are bringing you this
evidence, even the scientists ....
- Gigi Gordon, Exp., Court TV, September 28,1995.
Expert witnesses who testify to DNA evidence should have unbiased views
that are generally accepted by other respected members of their academic
communities. Moreover, with the guidance of the examiner, they must be
able to communicate scientific results and the meaning of these results
to a jury. The essential clarity of a convincing DNA result - a very
low probability of a random match to the DNA type found in the forensic
sample - can be obscured by an attorney or expert who loses the jury
in superfluous detail. Experts or attorneys who are unable to communicate
to the jury their clear and deep understanding of conclusions drawn from
DNA tests are liabilities.
Attorneys Represent the Evidence
. . . I'm going to try not to say things like substrate control
and reagent blanks and all that stuff. I'd like to talk to you about
it the way I talk about other things
- everything else in my life except for this science stuff.
- Marcia Clark, Ca. v. Simpson, September 28,1995.
Contrary to her intentions, Ms. Clark's statement, made in her closing
argument, weakened the prosecution's position. The State had the burden
of proof, and its most incriminating evidence was the product of scientific
work. Yet Ms. Clark suggested that the strongest evidence against Mr.
Simpson was not a normal part of life. A better approach would have been
to make the jury comfortable with the science through professionally
crafted, jargon-free explanations earlier in the trial. If the lead prosecutor
is not at ease discussing the State's best evidence, why should the jurors
take it seriously? Attorneys arguing cases based on scientific procedures
will increase the credibility of their evidence by advocating the technology
underlying it.
Human Sources of Error
There are three sources of investigational error: dishonesty, bias and
improper procedures.
Investigators, whether police officers or research scientists, are entrusted
with the honest reporting of work honestly conducted. Some do not meet
the ethical standard expected of them. Dishonesty means the fabrication
of data or the selection of actual data to support a desired result.
Bias is the selective assignment of relevancy to data which support a
preconceived idea. It often means subconsciously ignoring or overlooking
data which do not support one's view. Bias is a reality of all human
thought, and has many sources. It may arise for personal reasons, perhaps
the desire to prove a pet hypothesis. Or it may reflect a wish to fulfill
the expectations, implied or explicit, of a superior. Employees are sensitive
to such expectations, and see benefits from bringing the "good news" to
the boss. Sometimes the employee just knows the "right" answer
without being told.
Society has dealt successfully with limiting the effects of dishonesty
and bias in a variety of technical areas whose results affect the public.
For example, in the pharmaceutical industry an effective approach has
been to require that persons evaluating the effectiveness of a new drug
do not know which test samples contain the drug. This is called a "blind" study,
and it obviates bias because investigators do not know what the "expected" results
are. Blind analysis of forensic samples would reduce the possibility
of bias and dishonesty in police investigations and forensic samples
would reduce the possibility of bias and dishonesty in police investigations
and forensic testing. Stringent control of access to the evidence itself
as well as to the results of tests performed on it are of obvious importance.
Appropriate management and reporting structures for the various employees
involved in the development of courtroom evidence are essential. Ideally,
testing facilities would be independent of investigative agencies. All
attorneys trying DNA cases should be fully aware of the strengths and
weaknesses of the people and the processes upon which the quality of
the evidence depends.
Decision Making by Juries
Effective presentation of a case depends upon understanding and taking
full advantage of the decision-making process. How does a jury absorb
and use complex scientific evidence to reach a verdict?
Four factors determine the jury's understanding and use of scientific
evidence: clarity, timing, vividness and the emotional state of the jury.
No amount of instruction can convert a lay jury to an expert scientific
body, so why try? Jurors want the evidence to make a decision, and they
want it in as short a time as possible.
Jurors often reach a provisional judgment based on what they hear first;
they then reach a decision by modifying this position as further information
is presented. If a case is based on strong scientific evidence, it is
best to make the major points early.
Jurors decide based on information most vividly recalled. This may entail
what was most recently heard or most impressive. A long, tedious presentation
results in boredom, inattention and even disbelief.
Juries are traumatized by captivity, the onus of their responsibility
and the sometimes frightening details of the matters they are to decide.
Stress erodes the capacity to perform detailed intellectual tasks. Thus,
attorneys presenting science should seek to reduce jury trauma by being
brief, clear, confident and caring but dispassionate.
The Case Against Mr. Simpson
In Ca. v. Simpson, it was only physical evidence that placed
Mr. Simpson at the crime scene and connected him to the double homicide
of which he had been accused. The prosecution's case was founded largely
on the analysis of DNA contained in blood samples collected from the
crime scene, Mr. Simpson's vehicle and his residence. In her closing
argument, Ms. Clark epitomized the People's case as follows: We have
linked the defendant to the crime scene. We have linked the defendant
to the victims. We have linked the defendant and the victims to his car.
And that link has reached from Bundy into his bedroom at Rockingham.
They are all interwoven by time, by space, by occurrence, by science,
all linked.
- Marcia Clark, Ca. v. Simpson, September 26,1995.
These words suggested that science would be a firm ally of the prosecution
and a threat to Mr. Simpson's defense. Ms. Clark effectively articulated
the potential power of her case in her opening statement. The litany, "...
matches the defendant . . . matches the defendant .. . matches the defendant.
. . ." foreshadowed the results of DNA testing of blood evidence
that the State would introduce. Table 2 summarizes the prosecution's
physical evidence in the case. The table shows a potentially incriminating
set of findings, much of it based In DNA technologies developed in the
early 1980's and in forensic use in England since 1983 and the United
States since 1987.
The Prosecution's Tactics
Given the circumstantial nature of their case, the positive public image
of Mr. Simpson and the gravity of a first-degree murder charge, the prosecution
had to convince the jury that its strongest evidence, DNA testing, reliably
implicated Mr. Simpson. The burden of proof could be met only by a decisive
demonstration that the DNA evidence connected Mr. Simpson, the victims
and crime scene as Ms. Clark proposed. Moreover, to be most effective
in communicating with the jury, the DNA evidence had to be presented
early, vividly and clearly.
The prosecution began its case in January, 1995 with evidence supporting
its weakest argument, that two or three incidents of spousal abuse had
escalated to murder. The first testimony regarding DNA heard by the jury
was in April, and it came from the defense. During his cross-examination
of criminalist Dennis Fung, Robert Blasier demonstrated that Mr. Fung
had no understanding of or training in the collection and preservation
of DNA evidence. Thus, the defense had shown weakness in the DNA capability
of the Los Angeles Police Department (LAPD) before the prosecution had
even begun to describe its findings.
Following opening statements, the jury heard nothing from the State about
DNA until May. At that time, Dr. Robin Cotton of Cellmark Diagnostics,
the company that conducted DNA testing of crime-scene samples, took the
stand, Cellmark's results placed drops of Mr. Simpson's blood on the
leftside of a trail of bloody shoeprints leaving the scene of the murders.
The shoeprints had been made in Nicole Brown-Simpson's blood. Rather
than beginning with a concise statement of these results, prosecutor
George Clarke led Dr. Cotton into a two-and-a-half-day lecture on genetics,
biochemistry, molecular biology, proficiency-testing at Cellmark and
the minutiae of DNA analytical procedures. Contrary to its strategic
needs, the prosecution had given the jury the most complicated view possible
of forensic DNA testing and obscured the impact of its most incriminating
physical evidence.
The prosecution's tedious presentation of technical argot and its failure
to present the actual evidence early in Dr. Cotton's testimony was certain
to bore the jury. Since a bored jury disregards or disbelieves what is
boring it, the prosecution assumed the burden of boredom. Furthermore,
it alienated a jury already suffering from lengthy sequestration and
destroyed any possibility for a jury-prosecution alliance founded in
science. Paradoxically, this left the field open for the defense to supply
the scientific evidence expected by the jury from the prosecution.
The prosecution defended rather than asserted its case throughout the
trial. Although they had many investigational errors to deal with, by
describing each oversight in great detail, they effectively cross-examined
themselves. The inevitable effect of this repetition was to numb the
jury to the conclusions of the DNA analysis. To make matters worse, they
repeatedly told the jury that the mistakes of their investigators and
technical personnel had no effect on the reliability of the evidence.
Understating the effect of so many errors on the integrity of the evidence
was not credible. This further undermined the jury's confidence in the
prosecution and its evidence. As defense attacks on the physical evidence
escalated, the prosecution retreated from its most effective strategy
- the clear and cogent presentation of DNA evidence - and turned to an
emotional appeal to the jury based on charges of spousal abuse and the
savage nature of the murders. In effect, they sought revenge, but in
reality they distracted the jury from considering the evidence. The fact
that neither attorney delivering the People's closing argument had expertise
in DNA spoke for itself. Mr. Darden carefully developed the prosecution's
theory of spousal abuse leading to murder. Ms. Clark reiterated the prosecution's
rebuttals of defense attacks on the LAPD's handling of DNA and ended
with a plea for conviction accompanied by the soundtrack of a compilation
of Nicole Brown-Simpson's two famous 911 calls. Science had been lost
to the opposition.
Table 2
Main elements of the prosecution's physical case
Prosecution Exhibits |
Evidence |
Defense Response |
Blood drops at scene |
5 drops to the left of trail of bloody footprints: DNA match to Simpson
|
Sample DNA degraded; Simpson's DNA due to contamination by LAPD
|
One drop tested matched Simpson by seology |
1 drop on rear gate, DNA match to Simpson |
Planted by police |
RG's shirt |
Hair matching Simpson |
Poor crime-scene techniques |
Fiber matching sample on socks and glove found at Simpson's residence |
Poor crime-scene techniques |
Fiber matching mat of Simpson's vehicle |
Poor crime-scene techniques |
Knit cap at scene |
Human hair matching Simpson |
Poor crime-scene techniques |
Blood in Simpson's vehicle |
RG's blood on console |
Planted by police |
RG's blood on floormat in a bloody imprint consistent with the Bruno
Magli shoe |
Planted by police |
Simpson's blood near door handles |
Planted by police |
Socks in Simpson's bedroom |
NBS's blood: DNA match |
Sock planted by police |
Fiber matching sample found on RG's shirt |
Sock planted by police |
Glove forming a pair with one at crime scene found in alleyway at
Simpson's residence |
Hair of both victims |
Glove planted by police |
Blood of both victims |
Glove planted by police |
Fibers matching those found on RG's shirt |
Glove planted by police |
African American limb hair |
Glove planted by police |
Simpson's foyer and master bath |
Simpson's blood |
Irrelevant |
Simpson's person |
Cut on middle finger of left hand |
Cut on glass in Chicago after murders occurred |
The Defense's Tactics
To overcome the weight of the DNA findings, which implicated Mr. Simpson
in his wife's murder, the defense had to undermine the findings' impact
and question in their reliability. They proceeded to do so in a methodical
fashion.
The defense undermined the impact of the prosecution's DNA findings by
questioning the expertise of its key statistical witnesses, Dr. Bruce
Weir. In addition, Dr. Weir made a poor impression on the jury. He was
a passionate and vocal advocate of the increased use of forensic DNA
testing. He also vehemently disagreed on important statistical issues
with authors of the influential National Research Council report on Forensic
DNA testing, an established courtroom reference.
During Dr. Weir's cross-examination, the defense pointed out a systematic
error in his calculations, and he was obliged to revise all of his figures
as the jury watched. While numerically small, Dr. Weir's error succeeded
in raising questions in the minds of the jury about the ability of the
prosecution to provide undisputed statistical results. Moreover, by pointing
out a mistake in the prosecution's arithmetic, Peter Neufeld increased
the defense's scientific credibility with the jury. Although statistical
issues are centrally important to the forensic use of DNA testing, no
discussion of them appeared in closing arguments. Their significance
- a strong suggestion of Mr. Simpson's guilt - had been lost over long
weeks of testimony. The image of the combative Dr. Weir and his errors,
however, would remain long after the statistical dust had cleared.
The defense questioned the reliability of every article of DNA evidence
by one of two means: 1) proposing a conspiracy by the LAPD to manufacture
and plant evidence intended to incriminate Mr. Simpson; and 2) questioning
the competence of the LAPD by claiming that investigators, criminalists
and forensic scientists used inadequate procedures in the collection,
handling, storage and analysis of DNA and other evidence. Their witnesses
were confident, clear, vivid and factual. In addition, defense attorneys
never attacked the science but revered it, and they urged the jury to
do the same. "DNA is a sophisticated technology, it is a wonderful
technology," Barry Scheck told the jury, "but there is a right
way to dot it and a wrong way to do it." His implication was clear:
the LAPD's way was the wrong way.
Defense attorneys proposed conspiracy by alleging that the LAPD had identified
Mr. Simpson as the perpetrator soon after the crime. The police then
not only failed to carry out a thorough investigation of the crime scene
but also fabricated evidence to suggest his guilt. The testimony of Dr.
Henry Lee, Chief Forensic Scientist for the Connecticut State Police,
made these allegations credible.
Dr. Lee described a number of oversights by the LAPD in the recognition
and collection of evidence. In a brief examination of the crime scene,
he made striking discoveries of evidence overlooked by the LAPD: a bloody
imprint on the envelope containing the glasses Ronald Goldman was delivering
to Nicole Brown-Simpson and possible fingerprints on both the envelope
and a lens of the glasses within. In general, Dr. Lee's testimony demonstrated
a failure of the LAPD not only to recognize evidence but to manage the
entire crime scene as well. He concluded that, as a result, an accurate
reconstruction of what had transpired was impossible.
In addition, Dr. Lee addressed defense charges that the LAPD manufactured
key evidence - placing the glove at Rockingham and planting blood on
the socks and in Simpson's car. Evidence tampering was also suggested,
the defense argued, by stains on the wrapper of certain blood samples
sent to Cellmark from the LAPD. According to LAPD records, the samples
in question had been dried overnight on separate solid surfaces, housed
in separate tubes, and subsequently packaged together for shipment. Since
it is physically impossible for wet transfer to occur between dry samples
and their wrapper and since the time allowed for the samples to completely
dry was adequate, one could infer that some fresh, wet samples had been
placed among the previously dry ones. Such samples could have represented
material planted after the other samples had dried. Dr. Lee said in response
to cross-examination on this observation: "Only opinion [possible]...
under this circumstance - something wrong."
Dr. Lee's obvious love for his work, his delightful demonstrations and
positive attitude about science, and his concise, clear testimony communicated
neutrality and professionalism to the jury. His testimony built further
confidence in the defense's case.
Defense attorneys questioned the reliability of scientific evidence by
their unrelenting exposé of the incompetence of the LAPD and its forensic
laboratory. This exposé may have been the most important element of Simpson's
defense, by depicting the LAPD as a "cesspool of contamination," defense
counsel gave the jury reason to disbelieve any and all DNA evidence presented
by the prosecution. Incorrect procedures or deficiencies highlighted
by the defense at the LAPD's forensic DNA-testing facility are shown
in Table 3.
Table 3
Defense's List of Deficiencies in LAPD Procedures
1. |
No procedural manuals at LAPD labs |
2. |
No DNA training for evidence collectors |
3. |
No proficiency testing |
4. |
Lab neither inspected nor accredited |
5. |
No competent supervision of DNA work |
6. |
No records to establish chain of custody |
7. |
No security for evidence
Lens missing from glasses in envelope
Bronco without security for two months |
8. |
Failure to report errors in validation studies at LAPD |
9. |
Unsatisfactory sample handling
No paper on table Table not washed down |
10. |
Handling reference samples at same time and place as crime-scene
samples |
11. |
Trace evidence: moved bodies around (video, photos); blanket
from house placed over bodies |
Once it had established the incompetence of the LAPD, the defense moved
to discredit the prosecution's DNA results. The original DNA in forensic
samples found at the crime scene and in Mr. Simpson's car, they argued,
had so completely degraded that they were unreadable. Mr. Simpson's DNA
appeared in these samples, the defense suggested, due to contamination
from his reference sample collected and processed by the LAPD (310 in
Table 3). In effect, they implied that, due to deficient laboratory protocols,
Mr. Simpson's blood had been inadvertently added to a series of DNA-negative
forensic samples, and that error explained the prosecution's DNA-positive
results.
This point of view was corroborated by defense expert, Dr. John Gerdes,
who testified that any samples passing through the LAPD were suspect.
When Barry Scheck asked him,"... is the LAPD, in terms of levels
of contamination, worse than any other forensic laboratory you've ever
seen?", Dr. Gerdes replied, "Definitely, by far." Since
all the DNA samples in the case were processed at the LAPD before being
sent to Cellmark or the California Department of Justice laboratories,
the defense asked the jury in one stroke to discredit much of the prosecution's
evidence. These allegations were, however, speculative, particularly
regarding the specific details of whose blood was contaminating whose;
nevertheless, the defense's clear, vivid and methodical exposure of the
LAPD's inadequacies, the demeanor of its witnesses, and the prosecutions'
defensive criticism of its own evidence all raised serious doubts about
an otherwise incriminating circumstantial scientific case. As Barry Scheck
noted in his closing argument: "You cannot render a verdict in this
case of beyond a reasonable doubt on this kind of evidence, because if
you do, no one's safe - no one. The Constitution means nothing." The
Verdict The Simpson trial lasted one hundred fifty-nine days, and the
jury deliberated for less than four hours to find Mr. Simpson not guilty
of the charges. The speed with which they reached this verdict shocked
America.
Many observers felt that the quick decision was a slap in the face to
our system of justice, yet we must conclude that this is not so. Emotionally
charged accusations of racism coupled with the public's lack of understanding
of the science involved mask two key factors: the extent to which the
jury could believe the prosecution's case was compromised and the effectiveness
of the defense in communicating its case. Given the lackadaisical methods
and procedures used to collect, store and analyze the evidence, the statistical
uncertainty intrinsic to all DNA-based conclusions, the judge's instructions
and the defensive, tedious presentation of the prosecution's scientific
case, not guilty was a reasonable verdict. There were, however, other
important factors that influenced the jury's consideration of scientific
evidence in its decision-making process. In our next article, we will
examine a new model of jury decision making under conditions of stress,
Jury Trauma Syndrome, and will discuss the sources, uses and effects
of emotion in the Simpson trial and in a general courtroom context.
Sources and suggestions for further reading:
-
The primary sources for our work are trial transcripts available
on the internet. These include a number of in camera meetings
relating to juror dismissals, which provide a great many useful
insights: www.islandnet.com/~ walraven/ simpson.html
-
National Research Council, DNA Technology in Forensic Science, National
Academy Press, Washington, 1992. A good source for those interested
in an expert committee's view of the field. It includes both
legal and scientific matter.
-
Dershowitz, Alan M., Reasonable Doubts, Simon & Schuster, NY, 1996.
Chapter four of this thought-provoking work deals with the evidence
in the context of alleged police perjury. We disagree with some of
the interpretations given to the scientific evidence, but heartily
suggest the book to readers interested in this case because of its
thoughtful treatment of many important issues.
-
Coleman, H. & Swenson, E., DNA in the Courtroom A Trial Watcher's
Guide, GeneLex Press, Seattle, 1994. A simpler introduction to DNA
technology and its applications than the NRC report.
-
Rantala, M.A., O.J. Unmasked: The Trial, the Truth, and the
Media,
Catfeet Press, Chicago. An excellent compilation of the scientific
evidence. Its focus is refutation of the defense arguments.