Criminal Investigative Failures - Avoiding the Pitfalls (Part Two)
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Criminal Investigative Failures
Avoiding the Pitfalls (Part Two)
By D. KIM ROSSMO, Ph.D.
© brandXpictures
art one of this article the human mind. Individuals for patterns in, or drawing
P focused on cognitive
biases and how they can
contribute to criminal investiga-
often use heuristics—and suf-
fer from biases—when dealing
with probability. Police officers
inferences from, a small number
of incidents. For example, an
analyst examines the dates for
tive failures. Part two presents find it particularly hard to think a series of 15 street robberies
probability errors and organiza- probabilistically. Because of and observes that none of the
tional traps that can lead inves- their street experiences, they crimes occurred on a Thursday.
tigations astray. It also offers prefer black and white, rather Is this pattern meaningful?
recommendations and addition- than shades of gray. Probability Probably not. With only 15
al strategies that investigators errors in criminal justice most crimes, chances are at least one
may find helpful. often occur in the forensic sci- day of the week will be free of
ences but also can happen in robberies.
PROBABILITY ERRORS criminal profiling. Skeptics often say they do
Probability and Psychology not believe in coincidences.
Coincidences and the
Anyone who has spent a Law of Small Numbers However, when looking for
few hours watching people patterns within large numbers
gamble will realize that prob- A common problem with of items (i.e., events, suspects),
ability is a difficult concept for probability results from looking coincidences are inevitable.
12 / FBI Law Enforcement Bulletin
The comparison of Presidents While the similar crime char- a child murderer. Amongst other
Kennedy and Lincoln provides acteristics suggest a link, more details, the profile estimates the
a well-known example. The detailed examination reveals offender=s age and his vehicle
list of remarkable similarities important inconsistencies. One type, derived from automobile
is strictly the product of chance victim was a 3-year-old male, insurance data. Using the pro-
(with 43 U.S. presidents, 903 manually strangled, his body file, investigators evaluate two
possible comparisons are pos- found in a dumpster 100 yards suspects—one matches both
sible) and cherry picking (not- from his house. The other vic- the age and vehicle criteria, and
ing similarities, while ignoring tim was a 14-year-old female, the other only the age. Who
differences). strangled with a rope, her body is the better suspect vis-à-vis
What role does coincidence found dumped in a river 20 the profile? Actually, they are
play in major crime investiga- miles from her home. equal. Derived from the age
tions? If enough suspects are estimate, the vehicle type is not
looked at, by sheer chance, Double Counting an independent profile element
some will circumstantially ap- Extracting two elements of drawn from the crime scene (as
pear guilty. A few people will a crime from a common source opposed to a vehicle sighting
just be in the wrong place at the and then erroneously treating by a witness). Treating age and
wrong time. Efforts to solve a them as separate aspects can vehicle type as two separate
crime by “working backwards” mislead a criminal investiga- match points constitutes double
(i.e., from the suspect to the tion. A rumor heard from more counting.
crime, rather than from the than one person does not neces-
crime to the suspect) are suscep- sarily verify the information as Conjunction Fallacy
tible to errors of coincidence. If both individuals may have re- The conjunction fallacy
you look hard enough, you can ceived it from the same source. occurs when investigators as-
usually find some sort of con- Consider a behavioral profile of sign a higher probability to the
nection. These types of errors
often are seen in the proffered
“solutions” to such famous
cases as Jack the Ripper.
Coincidences can be a trap
when offender modus operandi
and similar fact evidence are
used for crime linkage pur-
“ In major cases,
particularly those
involving large
numbers of personnel
poses. Trawl search problems and extending over long
occur when only similarities, periods of time, internal
and not differences, are exam- rumors can pose a
ined.1 Comparisons of common significant problem.
similarities (e.g., vaginal inter-
course in rape crimes) lack util-
ity, while misspecifications of
similarities can be misleading.
Consider two juvenile murder
strangulations involving body
”
Dr. Rossmo, a former detective inspector in charge of the Vancouver, British
Columbia, Police Department’s Geographic Profiling Section, is currently a research
professor and director of the Center for Geospatial Intelligence and Investigation in
the Department of Criminal Justice at Texas State University in San Marcos.
transportation and concealment.
October 2006 / 13
overlap of two events than to ei- at only 38 percent. The prob- proportions of 16, 20, and 20
ther event separately. Probabili- ability that the offender was percent, and female offender
ties are combined by multiply- driving such a vehicle is only proportions of 9, 10, and 16
ing them together, resulting in a 28 percent (the probability the percent. According to the 2000
product smaller than either ini- witness actually saw the vehicle census, the U.S. population is
tial probability (given noncer- times the probability of witness 75 percent white and 49 percent
tainty).2 Conjunction fallacies accuracy). This does not mean male. So, while disproportion-
have occurred in DNA match- his information is not valuable. ately male, the only reason
ing, offense-linkage analysis, Obviously, suspect vehicles that most serial killers in the United
and crime forecasting.3 Imagine are gray domestic vans should States are white is because most
that a witness reports seeing a be prioritized and investigated. of the population is white. More
vehicle flee a nighttime gas sta- The problem only occurs when important, all else being equal,
tion robbery in which the clerk other suspect vehicles (e.g., blue serial killers are less likely to be
was shot dead. He states that he imported SUVs) are ignored. white in predominantly black
had only a quick glimpse but is or Hispanic areas.
reasonably sure the vehicle was
“
a gray domestic minivan. How Errors of Thinking
much weight should be placed Research has identified
on this description? A lack of two errors related to the issue
This question has two parts. understanding of of probability within the court
First, what is the probability base rates can lead context, the prosecutor’s fallacy
the witness actually saw the to misinterpreting and the defense attorney’s fal-
offender’s vehicle? In major research findings lacy.5 The prosecutor’s fallacy
crime cases, especially those and forensic occurs when people equate
involving significant publicity, results. the probability of the evidence
the public’s desire to help or given guilt with the probability
”
become involved is high, but of guilt given the evidence. Put
their information often proves simply, while all cows are four-
unreliable. A generous assump- legged animals, not all four-
tion gives the witness a 75 Base Rates legged animals are cows. This
percent chance of actually hav- A lack of understanding of error (known as transposing the
ing seen the robber’s vehicle. base rates can lead to misinter- conditional) can occur in both
Second, how accurate is his preting research findings and forensic science and behavioral
vehicle description? The wit- forensic results.4 Consider the profiling. This is illustrated by
ness provides three descriptive oft-quoted fact, “Serial killers the investigation into two bomb
elements. Assigning witness are usually white males.” While explosions that killed 21 people
accuracy probabilities of 70 technically correct, at least for and injured 182.6 Police officers
percent to the make, 90 percent the United States, this statement detained a group of men travel-
to the type, and 60 percent to is incomplete. To understand ing to a funeral and had their
the color (under some street- it properly, the relevant base hands examined for traces of ni-
lights, blue looks gray) puts the rates also must be considered. troglycerine. A forensic scientist
likelihood that the witness saw Three different studies of serial testified at their trial that he
a gray American-made minivan murderers found black offender was “99 percent certain” the
14 / FBI Law Enforcement Bulletin
defendants had handled explo- to the individual probabilities Organizational momentum,
sives. It was later disclosed, multiplied together) is very low. the inability to change direction
however, that many other sub- Consequently, the second part in the midst of a major investi-
stances could produce positive of the argument—that the evi- gation, is the converse problem.
test results, including nitrocel- dence is useless—is incorrect. To redirect and shift its focus
lulose found in paint, lacquer, from an established theory of a
playing cards, soil, gasoline, ORGANIZATIONAL crime or a particular suspect is
cigarettes, and soap. The de- TRAPS particularly difficult when an
fendants had played a game of agency has to admit publicly
Inertia, Momentum, that the original direction was
cards on the train shortly before
and Roller Coasters wrong. But, staying the course
their arrest. Their convictions
were overturned on appeal, Conservative in nature, law in light of compelling evidence
partly as a result of the foren- enforcement agencies can suffer pointing in a new direction
sic evidence being discredited from bureaucratic inertia, a leth- can prove catastrophic. Police
because the scientist had trans- argy or unwillingness to change, must strike a balance between
posed the conditional. © Corbis stability and responsiveness.
The defense attorney’s fal- The mistaken witness report
lacy occurs when evidence is of a suspect white van in the
considered in isolation, rather sniper attacks in the Washing-
than in totality. This type of ton, D.C., area serves as an
error happened during O. J. example. “It begs the ques-
Simpson’s preliminary hear- tion, did we publish composite
ing. The prosecution presented pictures because witnesses saw
evidence that blood from the the white van, or did we see the
murder scene, when analyzed white van because we published
using conventional grouping the pictures? We should’ve paid
techniques, matched the ac- more attention to the descrip-
cused, with characteristics tion of the Caprice and given it
shared by 1 in 400 people. The as much creditability as the van,
defense argued that an entire evolve, or act. Change is disrup- but we didn’t. In hindsight, it
football stadium could be filled tive and requires effort, energy, was a mistake made in the emo-
with people in Los Angeles who time, and money. Most depart- tion of the moment. But, with
also would match; therefore, the ments, however, have many all that we had set in place, we
evidence was useless.7 While competing demands with few, should’ve done better.”9
the first part of the defense if any, spare resources. Inertia Detectives working high-
argument regarding the number can slow an agency’s response pressure murder cases often re-
of matches is correct, only a to a new crime problem, as the fer to investigative roller coast-
limited number of those people Green River Killer case dem- ers, the ups and downs resulting
had relationships with the vic- onstrated.8 Police admitted that from the pursuit of prime
tims and even fewer had any they had no idea what they were suspects. A problem can occur if
reason for wanting to kill them. getting into when they began suspect “Jones” emerges dur-
The probability of an individual their investigation, which took ing the investigation of prime
filling all three categories (equal 20 years to complete. suspect “Smith.” Investigators
October 2006 / 15
typically see the viability of a the Washington, D.C., area (the and, therefore, receive most of
new suspect relative to exist- shooters drove a blue sedan). In their information secondhand.
ing ones, so if Smith is the best addition, some red herrings can Investigators need to out-
current suspect, then Jones is result from mischief or greed. line their assumptions. If an
relegated to a secondary status. During the Yorkshire Ripper assumption later turns out to be
When Smith is cleared, what inquiry in England, investiga- invalid, then everything follow-
happens to Jones? At best, Jones tors received three letters and ing from it must be rethought.
stays a secondary suspect; at a cassette tape from a person As the human mind does not
worst, he will be overlooked claiming to be the killer.12 automatically reevaluate infor-
altogether. Often discovered in Experts analyzed the voice on mation, specific organizational
cold case murder investigations, the tape and concluded that the procedures must be established
such suspects are obvious to the speaker likely came from the to address this issue. Document-
fresh eyes of new observers not same area postmarked on the ing assumptions facilitates this
subject to the psychological and letters. The tape was not from process and protects investiga-
organizational pressures that tions from “creeping credibil-
“
may have affected the original ity,” which occurs when an idea
investigators. or theory gains credence from
the passing of time, rather than
Red Herrings
and Rumors Fatigue, overwork, from supporting evidence. A
In high-profile cases, the
and stress, all endemic possibility hardens into a prob-
in high-profile crime ability and then crystallizes into
constant media attention brings “certain fact.”
forth a flood of public informa- investigations, also
can create problems Investigation teams must
tion, some of it relevant, most understand their knowledge
of it not. During the 3 weeks of for police personnel. base. They can assess valid-
the Washington, D.C., sniper ity only if they know the data
”
case, for example, authorities source. Otherwise, the informa-
received 100,000 calls, and tion may be a solidified rumor
more than 500 investigators or the product of creeping cred-
pursued 16,000 leads.10 In the killer, however, and the ibility. Some teams catalogue
such situations, the police run focus on this location—75 miles case information using three
the risk of landing a red her- north of where the real offender factors that can facilitate effec-
ring. Witness misinformation, lived—hurt the investigation. tive information sharing, allow-
compounded by organizational In major cases, particularly ing everyone (both present and
reluctance to accept that the those involving large numbers future) to work from the same
witness may be wrong, has sent of personnel and extending over foundation.
several high-profile investiga- long periods of time, internal
1) What they know (facts).
tions down the wrong path.11 rumors can pose a significant
Suspect vehicle sightings problem.13 A solidified rumor 2) What they think they
appear particularly problematic is gossip that has hardened into know (theories or
and include several infamous “fact” and taken as such by the conjectures).
examples, such as the white investigative team. Most vulner- 3) What they would like
box truck/van seen so often able are detectives who later to know (key issues requir-
during the sniper shootings in join a prolonged investigation ing additional data).
16 / FBI Law Enforcement Bulletin
Strategies to Help Avoid
Ego and Fatigue Investigative Failures
Ego, both personal and
organizational, can prevent an Encourage investigators to express alternative, even
investigator from adjusting to unpopular, points of view and assign the role of
new information or seeking devil=s advocate to a strong team member.
alternative avenues of explora- Consider using subgroups for different tasks and
tion. For example, a homicide facilitate parallel but independent decision making.
sergeant in a large metropolitan Recognize and delineate assumptions, inference
area told the author that his chains, and points of uncertainty; always ask, “How
detectives could decide within do we know what we think we know?”
5 minutes of arriving at a crime
Obtain expert opinions and external reviews at
scene who had committed the
appropriate points in the investigation.
murder and would be correct
95 percent of the time. While Conduct routine systematic debriefings after major
impressive, the remaining 5 crime investigations and organize a full-scale
percent equates to more than “autopsy” after an investigative failure.23
one missed call every month. Encourage and facilitate research into criminal
Therefore, detectives must have investigative failures and how they might be prevented.
the flexibility to admit their
mistakes and avoid falling into
the ego trap inherent in usually
being right. Stubbornness often the dominant theory, occurs in 3) Uniformity pressures:
coincides with ego and proves highly cohesive groups under conformity pressures (those
equally problematic. pressure to make important de- who disagree with the domi-
Fatigue, overwork, and cisions. First suggested after the nant views or decisions are
stress, all endemic in high-pro- disastrous Bay of Pigs invasion seen as disloyal); self-cen-
file crime investigations, also in Cuba,16 the main symptoms sorship (the withholding of
can create problems for police of groupthink include three dissenting views and coun-
personnel. Research has shown fundamental aspects. terarguments); shared illu-
that sleep can significantly 1) Power overestimation: sions of unanimity (silence
improve insightfulness.14 “It’s belief in the group=s in- is perceived as consent, and
necessary to be slightly un- vulnerability (resulting in an incorrect belief exists
deremployed if you are to do unwarranted optimism and that everyone agrees with
something significant.”15 Tired- risk taking); and belief in the group’s decision); and
ness dulls even sharp minds. the morality of the group=s self-appointed mind guards
Critical assessment abilities purpose (leading to ignoring (individuals who elect to
drop in overworked and fa- the ethical consequences of shield the group from dis-
tigued individuals, who start to decisions). senting information).
engage in what has been termed 2) Close-mindedness: group Groupthink has several
“automatic believing.” rationalizations; discredit- negative outcomes that spell di-
ing of warning signs; and saster for a major investigation.
Groupthink negative stereotyping of the Victims of this trap selectively
Groupthink, the reluctance group’s opponents (e.g., evil gather information and fail to
to think critically and challenge or stupid). seek expert opinions.17 They
October 2006 / 17
neglect to critically assess their Prosecutors and judges, as well “without fear or favor.” That
ideas and examine few alterna- as police officers, can fall prey task, integral to both public
tives, if any, and do not develop to these traps.21 Training is an safety and justice concerns,
contingency plans. important first step, but insuf- must be conducted in an unbi-
ficient by itself. Effort and ased and professional manner.
RECOMMENDATIONS vigilance also are required. Law When it is not, the result is un-
Police investigations can enforcement agencies need to solved crimes, unapprehended
significantly benefit from the create formal organizational offenders, and wrongful convic-
thoughts and opinions of inde- mechanisms to prevent these tions. Understanding what can
pendent experts. The British subtle hazards from derailing go wrong is the first step toward
Home Office, frustrated over the criminal investigations. preventing a criminal investiga-
lack of progress in the Yorkshire tive failure.
“
Ripper murder inquiry, formed
an external review committee Endnotes
that included a civilian forensic 1
D.M. Risinger and J.L. Loop, “Three
scientist who studied the loca- Police investigations Card Monte, Monty Hall, Modus Operandi
tions and times of the crimes can significantly and ‘Offender Profiling’: Some Lessons
and correctly concluded where benefit from the of Modern Cognitive Science for the Law
the killer lived (despite the mis- thoughts and opinions of Evidence,” Cardozo Law Review 24
leading letters and cassette tape (2002): 193-285.
of independent 2
There is an assumption of indepen-
mentioned earlier).18 experts. dence of events.
Outside review also can 3
“Crime Analysis Challenge,” Crime
”
play an important role. Police Mapping News 4, no. 3 (2002): 9-13.
procedures in the United King- 4
B. Robertson and G.A. Vignaux, In-
dom require an independent terpreting Evidence: Evaluating Forensic
CONCLUSION Evidence in the Courtroom (Chichester,
review of unsolved homicide England: John Wiley and Sons, 1995); and
cases after 1 year.19 This pro- Thankfully, most criminals A. Tversky and D. Kahneman, “Evidential
duces two results. First, knowl- are not masterminds, and, in Impact of Base Rates,” in Judgment Under
edge of this policy prompts de- many cases, the criminal in- Uncertainty: Heuristics and Biases, eds.
tectives to leave no possibilities vestigation is a straightforward D. Kahneman, P. Slovic, and A. Tversky
(Cambridge, MA: Cambridge University
unexplored. Second, external process. However, a major Press, 1982), 153-160.
reviewers are more apt to notice crime “whodunit” can be chal- 5
Supra note 4 (Robertson and
mistakes and omissions. This is lenging and difficult. Certain Vignaux).
the same basis as scholarly peer factors identified with cognitive 6
Supra note 4 (Robertson and Vig-
review, a foundation of scien- and organizational failures (low naux); and B. Woffinden, Miscarriages
of Justice (London, England: Hodder and
tific research. information levels, limited re- Stoughton, 1988).
As a final warning, research sources, and pressure to obtain 7
Supra note 4 (Robertson and
has suggested that even when quick results) 22 are all too com- Vignaux).
8
individuals are aware of these mon in these investigations. C. Smith and T. Guillen, The Search
problems, they still find them The criminal investiga- for the Green River Killer (New York,
NY: Penguin Books, 1991).
difficult to overcome. The dan- tion process plays an important 9
B.J. Karem and C. Napolitano, “In
gers are especially great in high- and special role in countries a Room with Madness,” Playboy, March
profile cases of horrific crimes, governed by the rule of law. 2003.
20 10
such as sex or child murders. Its function is to seek the truth, Ibid.
18 / FBI Law Enforcement Bulletin11 16
A. Campbell, The Campbell Inquiry Yale research psychologist Irving in Crime Science: New Approaches to
Report: Bernardo Investigation Review Janis. Preventing and Detecting Crime, eds. M.J.
17
(Toronto, ON: Government of Ontario, Department of Justice, Canada, FPT Smith and N. Tilley (Cullompton, England:
1996). Heads of Prosecutions Committee Working Willan Publishing, 2005), 191-207.
12 23
R.H. Doney, “The Aftermath of the Group, Report on the Prevention of Miscar- For example, the Vancouver, British
Yorkshire Ripper: The Response of the riages of Justice (Ottawa, 2004). Columbia, Police Department assigned a
18
United Kingdom Police Service,” in Serial S.S. Kind, The Scientific Investigation deputy chief constable to review thor-
Murder: An Elusive Phenomenon, ed. S.A. of Crime (Harrogate, England: Forensic oughly what happened, as well as what
Egger (New York, NY: Praeger, 1990), Science Services, 1987); and The Sceptical failed to happen, after a problematic serial
95-112. Witness (Harrogate, England: Hodology, murder case.
13
Studies of rumor propagation have 1999).
19
shown that as a rumor spreads, its dramatic While many other factors are
components are exaggerated, while its involved, it is perhaps worth noting that Over the course of his 21-year policing
qualifiers diminish or disappear altogether; homicide clearance rates in the United career, the author worked assignments
see, T. Shibutani, Improvised News: A Kingdom are over 90 percent compared in organized crime intelligence, emer-
Sociological Study of Rumor (Indianapolis, with 63 percent in the United States. gency response, patrol, and crime pre-
IN: Bobbs-Merrill, 1966). 20
R.J. Heuer, Central Intelligence vention. His interest in the subject of
14
U. Wagner, S. Gais, H. Haider, R. Agency, Center for the Study of Intelli- criminal investigative failures originates
Verleger, and J. Born, “Sleep Inspires gence, Psychology of Intelligence Analysis from various unsolved major crime
Insight,” Nature 427 (2004): 352-355. (Washington, DC, 1999). cases for which he has consulted. Cur-
15
Dr. James Watson, Nobel Laureate 21
Supra note 17; and P. de C. Cory, rently, he is working on a book on the
in Medicine and codiscoverer of DNA=s The Inquiry Regarding Thomas Sophonow topic. He thanks those detectives who
molecular structure, commenting on the (Winnipeg, MB: Queen=s Printer, 2001). willingly discussed what went wrong in
importance of unstructured time in 22
P. Stelfox and K. Pease, “Cognition their investigations and dedicates this
thinking. and Detection: Reluctant Bedfellows?” article to them.
Snap Shot
Call of the Wild
The sound of sirens at the scene of an accident attracted and confused two coyotes.
Photos submitted by Peter A Marchica, III and taken in Joshua Tree, California.
October 2006 / 19You can also read
