Before reading this post, please read Part 1, which presents the evidence that sequential lineups are more
accurate than simultaneous lineups.
Why do the police prefer the simultaneous method? First, it produces more identifications, which
is their immediate goal. Since they are likely to believe that
whomever they have arrested is the guilty party, they argue that the
greater number of misses by the sequential method results in guilty
suspects being allowed to go free, roam the streets, commit further
crimes, etc. They are not as sensitive to the costs of false
alarms since they underestimate how often they occur.
In his statement refusing to adopt
sequential lineups, Mr. Bucar refers to a meeting of the National
Academy of Sciences (NAS) in which there was “dissent among
scientists who claim that the analysis methods used in the research
between 2009 and 2011 was faulty and when corrected will actually
show that . . . the simultaneous method is superior.” NAS's
Committee on Science, Technology and Law held three meetings on
eyewitness identification in 2013 and 2014. The program of these meetings, along with slide shows submitted by the participants, is available online. However, I couldn't determine the exact nature of
the controversy to which Mr. Bucar refers. I am puzzled by his
reference to analysis methods used between 2009 and 2011, since I
don't detect any change in methodology. NAS is preparing a report on
eyewitness identification to be released in the near future. I've
signed up to receive a copy and I'll let you know their recommendations.
Meanwhile, here's my best guess as to
what Mr. Bucar is concerned about. One of the great unknowns in the
real world use of eyewitness identification is the base rate of culprit-present lineups. What percentage of lineups actually
contain the prepetrator? Is it 50%? 75%? 90%? Neither the
identification rate nor the conviction rate really answer this
question.
In the studies referred to earlier, the base rate is 50%, since the researchers run
an equal number of participants with culprit-present and
culprit-absent lineups. In the real world, the lower the percentage
of culprit-present lineups, the greater the danger of false alarms.
For example, suppose the police conduct a near-random sweep of the
neighborhood and show eyewitnesses many people who are not identified
as suspects by any other type of evidence. Under these
circumstances, it becomes more important to use the sequential
method.
The police probably believe that close
to 100% of their lineups are culprit-present. If they are right, the
number of true identifications—or more likely, lucky guesses—lost
in these culprit-present lineups using the sequential method might
exceed the number of false identifications avoided in the
(presumably) smaller number of culprit-absent lineups. Using Bayes'
theorem, Steven Clark has identified the crossover point at which the
misses exceed the false alarms using the sequential method. If the
true base rate is greater than 85%, the simultaneous method will
identify more guilty suspects.
Of course, no one will ever know what
the true base rate of culprit-present lineups is. Your guess is
likely to be influenced by whether you trust the fairness and
efficiency of police investigative procedures or are more skeptical.
One of the more important contributions of DNA testing is that it has
greatly increased our estimate of the number of innocent people who
are convicted of crimes in this country.
However, simply comparing the rate of false alarms in the simultaneous condition to the rate of misses in the sequential condition doesn't do justice to the true superiority of the sequential method because a false alarm is a more costly error for society than a miss. In both cases, the real culprit escapes detection, but when a false alarm occurs an innocent suspect is likely to be arrested and charged, with costs to that individual that range from considerable inconvenience to the complete ruin of his or her life. This is presumably the basis of Lord Blackstone's famous quote: “It is better that ten guilty men escape than that one innocent suffer.”
In a classic case of bad timing,
Allegheny County police recently released a man arrested based on a
mistaken identification from a culprit-absent lineup using the
sequential procedure. Another man confessed to the crime. Of
course, no one claims the sequential procedure is foolproof. Our best guess is that, when the culprit is absent, it will produce false
alarms almost one-third (32%) of the time, which is disturbing, but
not as bad as the 54% false alarm rate using the simultaneous
procedure.
On July 31, Pittsburgh public safety director Stephen Bucar had an unpromising first day on the job. A
week before, Allegheny County District Attorney Stephen Zappala sent him a letter requesting changes in the way the Pittsburgh city police
conduct eyewitness identifications. Mr. Zappala said his office
would no longer prosecute cases unless (1) the identification was
made using a sequential rather than a simultaneous
lineup and (2) the lineup was conducted by an officer not involved in
the investigation. His demand may have been motivated by an abstract
desire for justice, but it's more likely the result of two recent
lawsuits filed by men who were mistakenly arrested based on faulty
identifications using the simultaneous method.
But the Pittsburgh police, notorious
for their resistance to change, said something like, “That's not
how we do things around here.” Unfortunately, Mr. Bucar decided to back them up, citing what he believes to be conflict in
the scientific literature over whether sequential or simultaneous lineups are more likely to lead to error. This is disappointing news for
those of us who had hoped new Mayor Bill Peduto would bring more rationality to Pittsburgh government.
Stipulating that the identification
be conducted by an officer not involved in the case assumes that this
officer won't know which person in the lineup is the suspect. If so,
this double blind procedure prevents bias in which the
administrator unintentionally communicates the identity of the
suspect to the eyewitness. Since Mr. Bucar did not mention blind
testing in his statement, I presume he has no objection to it.
When an eyewitness views a lineup,
there are four possibilities. The culprit is either present in or
absent from the lineup, and the eyewitness either does or does not
make an identification. If the culprit is present and the eyewitness
correctly identifies the culprit, this is called a hit. When
the eyewitness either identifies someone else or makes no
identification, this is a miss. When the culprit is absent
and the eyewitness erroneously makes an identification, this is a
false alarm. Failure to identify anyone is a correct
rejection. Obviously, the goal is to maximize hits and correct
rejections, thereby minimizing misses and false alarms.
Culprit Present
Culprit Absent
Identification
Hit
False Alarm
No Identification
Miss
Correct Rejection
In the traditional simultaneous
procedure, the eyewitness is shown an array of (usually) six
photographs and asked which one, if any, is the perpetrator. In the
sequential procedure, the eyewitness is shown the photographs one at
a time, and is asked to state whether each one is the perpetrator.
In this procedure, eyewitnesses usually don't know how many photos
they will be shown.
In studies that compare these methods,
participants unexpectedly witness a simulated crime, either live or
on video, and are later asked to make an identification. In those
studies with complete designs, the perpetrator is present in
half the lineups, while in the other half, he or she is absent. Half
of each of these lineups are conducted using the simultaneous and the
sequential procedure. Since the researchers know whether the culprit
is present in each lineup, they can determine whether a correct
identification was made.
Several decades of research show the
sequential procedure to result in greater accuracy. In 2011, Nancy Steblay and her colleagues published a meta-analysis of all 72 known
studies (from 23 labs involving over 13,000 participants) comparing
simultaneous and sequential lineups. Simultaneous lineups produce
higher choosing rates (76%) than sequential lineups (61%), suggesting
than the simultaneous method encourages guessing. More importantly,
identifications from a sequential lineup contain fewer errors.
To illustrate this, here are the data from the 23 studies with complete designs (as described above).
Since all four conditions are present in these studies, it is
possible to compare their average results.
Hits from culprit-present lineups
Simultaneous 52%
Sequential 44%
Difference 8% fewer hits in
sequential
False alarms from culprit-absent
lineups
Simultaneous 54%
Sequential 32%
Difference 22% fewer false alarms
in sequential
There is a tradeoff. If all lineups
were culprit-present, the simultaneous method might appear to be
superior, since it produces 8% more identifications. However, since
the simultaneous method encourages guessing, some researchers argue
that this 8% difference should be treated as lucky guesses rather
than true identifications. When the culprit is absent, the
simultaneous method leads to 22% more false alarms. Therefore, the
sequential method is more accurate.
Why is the simultaneous method more
error prone? When an eyewitness is asked to view a lineup, he or she
probably infers that the police think they have arrested the
perpetrator. In a simultaneous array, eyewitnesses make a relative
judgment. They compare the photos to one another and choose the
one which most closely resembles their recollection of the
perpetrator. In the sequential method, however, because they don't know how many suspects they will be shown, they must make an absolute
judgment, comparing each suspect to their independent memory of
the perpetrator.
Here is a 61-min lecture by researcher Gary Wells
that I posted once before. Between minutes 14 and 30, he talks about
the relative judgment process and the need for sequential lineups.
One of my guilty pleasures is watching
auto racing on television, an interest that traces back to my
childhood, when my father took us to midget, sprint car and stock car
races throughout the Northeast. Auto racing suffered a tragedy this month when Tony Stewart, three-time NASCAR Sprint Cup champion,
driving a sprint car on a dirt track in Canandaigua, NY, ran over and
killed fellow-driver Kevin Ward, Jr., who was standing on the track.
The incident was unusual only by virtue of its sad ending.
In racing, it's common for contact to
occur when one car passes another. It doesn't always cause a
accident, but when it does, it is most often the slower car that is
left spinning to the side of the track. The passing driver typically
denies that the accident was intentional; his victim usually has a
different interpretation. It is not unusual for the victim to
exhibit signs of road rage, for example, standing on the track and
yelling or shaking his fist at the other driver as he passes the
scene of the accident.
On the lap prior to the fatal accident,
Stewart (#14) spun out Ward's (#13) car, bringing out the caution flag. The
video shows what happened next.
You can hear Stewart hit
the throttle just before he drives past Ward. (The video doesn't
permit us to locate the source of the sound, but eyewitnesses claim it was Stewart.) Stewart may have responded to Ward's anger with
some road rage of his own. On a dirt track, drivers will sometimes deliberately spray
dirt onto someone standing on or near the track. However,
accelerating suddenly on dirt can cause the car to fishtail, sending
its rear wheels toward the outside of the track. Stewart's right
rear tire struck Ward, pulled him under the vehicle, and killed him.
Stewart's actions were reckless but
almost certainly not intentional. It's doubtful that he will be
prosecuted, since Ward assumed a great deal of risk by walking on the
track. He may, however, suffer professional consequences, especially
given his long history of on-track aggression. (For example, when
Stewart was taken out in an accident he attributed to fellow NASCAR
driver Matt Kenseth, he threw his helmet at
Kenseth's front windshield. Later he threatened Kenseth with
retaliation in a television interview.) Stewart's greatest risk will
be loss of corporate sponsorship and income from television
commercials.
AAA reports that aggressive driving,
broadly defined, is a factor in 56% of fatal auto accidents. A 2013 article by Christine Wickens and her colleagues summarizes what is
known about the causes of road rage, which they define more narrowly
as aggressive actions on roadways resulting from hostility toward
another driver. Since little is known, the article functions as a
road map for future research. They divide the causes into personal,
i.e., men exhibit more road rage than women, and situational,
i.e., it occurs when aggressive intent is attributed to
another driver. Not mentioned among potential causes is
observational learning and imitation of the behavior of role models.
NASCAR and other racing sanctioning
bodies have been quite tolerant of aggressive displays on the track,
probably because they think they increase the sport's popularity.
But drivers like Tony Stewart are liked and respected by racing fans,
and their actions might serve to legitimize similar aggressive
actions on the roadways. Are changes in the popularity of auto
racing on television correlated with changes in the frequency of
aggression on our highways? (NASCAR's ratings have tailed off in recent years. Has road rage also declined?)
There has been relatively little
research on the effects of specific events shown or reported in the
mass media. An exception is research on suicide contagion, a problem
which has become timely following the death of Robin Williams.
Suicides increase in the country in the week following the suicides of well-known people. The effect is greater when person who commits
suicide is real rather than fictional and there is evidence
suggesting that contagion is more likely to occur when there is a
demographic match between the model and his or her imitator. These
studies could point the way for future research on the connection
between televised incidents and road rage among racing fans.
The Stewart incident has brought about
at least a temporary change. NASCAR has announced that drivers will
not be permitted to leave their cars following an accident until they
are escorted off the track by the safety crew. (Of course, there are
exceptions, such as when the vehicle is on fire.) NASCAR claims that
this has always been the rule, but if so, it hasn't been enforced.
If this change is permanent, it could impact not only driver safety,
but audience safety as well.
Now, NASCAR, what about those threats
of violence in post-race interviews?
In spite of declines in violent crime during the past two decades, the United States imprisons more people than any other country in the world, and at any time in its history. Our punitive criminal justice policies have had a grossly disproportionate impact on racial minorities. While African-Americans make up 12% of the population, they are 40% of our criminal inmates. These disparities exist even where evidence suggests there are no racial differences in commission of the offense.
Both President Barack Obama and Attorney General Eric Holder have argued for reducing the length of prison terms for nonviolent offenses, giving racial disparities in incarceration as one of their reasons. The President commented on this issue when the administration announced new guidelines for public school discipline intended to reduce racial disparities in school suspensions and dropout rates.
I remember thinking at the time that this argument could backfire. In a racist society, stating racial discrimination as a reason to reduce mass incarceration carries the risk of increasing support for punitive crime policies. Ian Haney-Lopez has noted that get-tough crime policies are a "dog whistle" used by politicians to appeal to white prejudice without referring directly to race. These coded racial appeals are used because they are effective. A new article by two Stanford social psychologists, Rebecca Hetey and Jennifer Eberhardt, supports these speculations.
Hetey and Eberhardt note that racial disparities in imprisonment are usually treated as an unintended outcome of punitive policies. They propose instead that knowledge of racial discrimination in the criminal justice system is one of the causes of widespread public support for these policies. They conducted two field experiments.
In the first, white registered voters were approached by a white female experimenter at a train station and asked to sign a petition for a ballot initiative to reduce the punitiveness of California's "three-strikes-and-you're-out" law. Before being presented with the petition, participants were shown a 40-sec video about the prison system. The video did not refer to race, but in one version, 25% of the inmates shown were black, while in the other version, 45% were black. As predicted, fewer people (27%) were willing to sign the petition in the More-Black condition than in the Less-Black condition (52%).
The second study was an online survey of white New York City residents conducted by Survey Sampling International. Near the beginning of the survey, participants were given demographic information stating that the prison population was either 40.3% or 60.3% African-American. (Both statements were true. The first referred to the U. S. prison population, while the second referred to New York City.) Later in the survey, participants were shown a petition calling for an end to the New York police's "stop-and-frisk" policy, and asked whether, if they had been approached, they would have signed it. The results confirm those of the first experiment.
A measure of fear of crime was included in the survey. The relationship between racial composition of the prison population and support for less punitive policies was mediated by fear of crime. That is, the More-Black condition produced greater fear of crime, which led to less willingness to sign the petition. However, this was not the whole story. The effect of racial composition on policy acceptance was statistically significant even when fear of crime was statistically eliminated.
The authors admit that their results pose "quite a challenge for those striving to create a more just and equal society." It appears that presenting people with evidence that a social policy leads to racial injustice has the effect of increasing, rather than reducing, support for the policy. Maybe the President should emphasize the fact that reducing the prison population would save money.
