Witness Credibility Assessment
In addition to determining if a person is an eyewitness, a corroborative witness, an independent
witness, a competent witness, or a compellable witness, every person who is a witness during an
investigation needs to be subjected to a credibility assessment. As information and evidence are
collected from each witness, it is part of the investigator’s job to determine the level of
confidence that can be attributed to each witness. This is called witness credibility assessment.
One of the most significant issues to be considered in assessing a witness is determining if they
are a witness, or if they are a suspect posing as a witness. More likely than interviewing false
reporters of crime, investigators find themselves interviewing a variety of ordinary people who
truly have been the victim of a crime, have witnessed a crime, or witnessed some aspect of a
criminal event. The level of confidence an investigator can have in a witness will be contingent
on several factors relating to who the witness is, the abilities of the witness, and the
circumstances of the event.
1. Witness profile. Ideally, every witness would be an upstanding member of the
community with a high level of integrity and an outstanding reputation. This is rarely the
case. The nature of criminal activity and the natural proximity and association of criminals
within a criminal community, often skew the witness list more towards those with more
colorful and less upstanding personal profiles. Being part of the criminal community, or
having a criminal record, does not necessarily mean that a witness will not be truthful.
However, these are factors that an investigator must consider when assessing the value of
the evidence being reported. For example, if a witness has a record for perjury, their
evidence should be carefully scrutinized and additional corroboration may be required to
strengthen the witness’ account of the events to achieve acceptable credibility for the court.
2. Witness bias – motivation to lie. As discussed earlier in this chapter, independent witnesses
who are not connected to the victim, the accused, or the event itself make the most credible
witnesses. People close enough to a criminal event to become witnesses are often, in some
way, related to the victim, the suspect, or to the event itself. As such, the associated witness
may have a bias in making their report of the event. As a friend or foe, the witness may have
some motivation to withhold information or to lie to influence the outcome. Understanding
how each witness fits into the event, and what their linkages are to other participants or the
event itself, is an important dynamic to uncover. In the case of a bias witness, additional
corroboration should also be looked for.
3. Witness involvement – emotional impact of the event. Criminal events can be very
stressful and anxiety producing experiences. This is not only true for the victim but for anyone
who has been exposed to danger, violence, or situations where threats to personal safety or
incidents of injuries or death have occurred. As human beings, we are not conditioned to live
through these kinds of events without experiencing some kind of emotional response. Post-
Traumatic Stress Disorder speaks directly to the emotional damage traumatic events can inflict
(Resnick, Kilpatrick, Dansky, Saunders, & Best, 1993). It is important for an investigator to
consider the nature of the event and the exposure of the witness to these dynamics. Extreme
post traumatic trauma, such as observing the violent death of a loved one, can sometimes
render that witness unable to provide a reliable account of details (Streets, 2011). It may be
necessary to give some witnesses time to regain their composure to provide information or
evidence. In some cases, the traumatic effect is too significant and the information cannot be
recovered. Knowing how a witness is connected to the event and being able to comprehend
their potential exposure to emotional trauma provides the investigator with the insight that
certain strategies, such as softer interview techniques, flexible timing, and professional support
resources that take the emotional trauma of the witness into consideration, may be necessary
and appropriate. Another kind of emotional trauma is a witness’ fear for their personal safety.
This can be a fear of physical, psychological, or emotional reprisals for the witness providing
evidence. In a situation that includes organized criminal groups, this fear is a genuine and
understandable concern. In these types of cases, it may be difficult to protect the identity of a
witness, and assurances of protection of the witness can be subject to jurisdictional or
organizational limitations of witness protection resources.
Location when viewing the event
A witness’ physical location when observing an event can become an important point of
evidence, and should be considered and included in the interview and statement of each witness.
If a witness is providing details of the event that required them to be in direct proximity of the
accused or the event to observe or hear, the physical location of the witness at the time of those
observations is a critical element. Physical location can also be important in explaining gaps or
differences in witness observations. The fact that one witness to a crime observed certain
actions, but another witness did not, can sometimes be explained by the alternate angles of
observation of each witness or because of some physical obstruction that affected one witness
but not the other. Crime scene photos and diagrams can often help witnesses to demonstrate and
describe their distinct perspectives. Returning to the scene of the crime to physically establish
these locations and angles of observation can be a useful exercise for investigators to conduct.
Length of observation time Very simply, length of observation time is the amount of time a
witness had to see the event taking place. This amount of time will vary with circumstances, as
there would be a difference in opportunity for observation between one witness standing
stationary at the crime scene observing the event, and another driving past the unfolding events
at 100 kilometers per hour. This can also be an issue contingent upon the awareness of the event
taking place. Some witnesses become aware of the event more quickly and have a longer
opportunity to observe. As with our example of the bank robbery, the teller being robbed had the
longest observation time, the customer immediately behind the robber became aware that
something was happening and had a shorter observation time, but the third customer did not
become aware of anything until the robber bumped into him. This scenario demonstrates the
value and detail of evidence an investigator might expect from witness with differing levels of
observation time.
Time elapsed between the event and the interview.
A critical aspect of gaining the best account of events from any witness is making sure that the
interview happens at the earliest opportunity. It is a practice in police investigation to make
every effort to identify and interview witnesses as soon as possible. As a simple exercise to
demonstrate the importance of finding and interviewing witness quickly, take a piece of paper
and to the best of your ability, write down the details of your day starting at the beginning of the
day three days ago. What did you do? Where did you go? Who did you see? If you are like most
people, you have some level of daily structure to your life. From that structure, perhaps you will
recall you got out of bed at a usual time. Maybe you went to work or stopped at the gym or at
your favourite coffee shop on the way to work. These benchmarks of your daily routine may be
easily remembered. But, on your way to work, did you happen to see a green van with extensive
damage to the front end on the street near your home? Of course, this is a fictitious question, but
this would be the kind of inconsequential daily observation information you might be asked to
recall by police canvassing for witnesses to a crime.Understanding this time limited aspect of
human memory, investigators need to consider how much weight they can place on the accuracy
of information being recounted by a witness. If a witness is providing a remarkably accurate
recollection of something being recounted from any distance in the past, it is a good idea to ask
that person how they can recall what should be a mundane event with such a degree of accuracy
or clarity. If they are correct, the witness will sometimes provide a memory trigger that made
them notice and causes them to recall. For example, a witness may answer, “Yes, I remember
that green van with all the damage to the front end because my brother has a green van just like
that and I looked at the driver and saw that it wasn’t my brother. I looked at it even closer
because I had never seen that van on my street before.”
Ability to record or repetitively recount details
If a witness was aware that they had witnessed a crime and they were making a conscious effort
to record or otherwise memorize the facts, this is a point that the court will be interested in
hearing as part of the witness’ evidence. If, for example, to remember the licence number of a
suspect vehicle, the witness repeated the number over and over until they were able to write it
down, this is an important detail that should be recorded in the witness statement, and the paper
upon which the number was written should be seized and retained as an exhibit that can be
shown to that witness on the stand as the note they made at the time of the event. This
demonstrated that the witness had intent to recall and record the details of an event, which will
contribute in a positive way to the credibility of the witness.
Physical abilities – hearing, sight, smell, touch, taste and cognitive perception
The physical faculties of the senses may be used by a witness in their recollection of the events
they are describing. When a witness makes a statement referring to their senses, their credibility
in giving that evidence will depend upon the extent to which their senses are working. In taking
statements from witnesses, the investigator must be satisfied that a witness who claims to have
seen an event has adequate vision to make that observation. Similarly, a person who states that
they heard something must be able to demonstrate that they have adequate hearing to have heard
it. Speaking very quietly to test the hearing limits of a witness or asking a witness to describe
something within the visual ranges of the evidence they saw are both reasonable strategies to
informally test a witness’s range or limitations of senses. Asking a witness questions about their
use of eyeglasses, contact lens, or hearing aids during their observation of events are all
reasonable strategies to establish the credibility of a witness to make the observations they are
reporting. Flowing from the use of their senses, witnesses will often provide information and
cognitive perceptions of the events they witnessed. The cognitive perceptions of a witness are
their own personal interpretation of the information they took in through their senses. As such,
they are a subjective analysis of the information being sensed. A witness may provide a
statement regarding the age of a suspect, the size of an object, the speed of a vehicle, the smell
of alcohol on a person’s breath, or even the distance they stood from the event they witnessed.
To a certain degree, the court will allow such evidence and opinions of common knowledge
from non-expert witnesses; however, a witness may be challenged on their observations, and it is
best to understand any misperceptions in advance. Again, informal testing of a witness to
become comfortable that their cognitive perceptions and subject interpretations are accurate and
not significantly skewed is a reasonable way to test credibility. For estimating the age of a
suspect, an investigator could ask the witness to point out other persons who are approximately
the same age. Similar tests could be undertaken in testing perceptions of the size of objects, the
speed of vehicles, and the distance to locations. For statements regarding observations, such as
the smell of alcohol, the investigator should ask the witness to describe their personal
experiences with alcohol to know that it was alcohol they smelt. If the witness had not
experienced alcohol or been with people who were drinking alcohol, that opinion of smell would
lose credibility.
Cognitive capacity and age of witness
To establish the competency of either a child or a person of limited mental capacity, conducting
a careful witness credibility assessment will be helpful for the prosecution in meeting challenges
to competency. Part of the initial interview should seek to determine if the child or person of
limited mental capacity understands the need to tell the truth. The competency background of the
witness should be conducted by interviewing persons, such as parents, caregivers, teachers, or
doctors, who know the witness and can attest to their mental capacity and their ability to
understand questions and communicate their answers.The actual interview of both children and
persons of low mental capacity are a delicate and time-consuming process. They must be
conducted in a manner that is both suited to the maturity level of the witness, and structured
using non-leading questions to elicit answers. In cases where it is possible, investigators with
specialized training in this type of interviewing should be utilized. That said, in the first instance,
at the scene of an event, it is important for the responding investigator to understand the special
considerations that apply to this type of witness in consideration of their evidence. The goal in
these cases is to determine how much weight can be attributed to the evidence being provided by
witnesses. An investigator may determine that the evidence of a witness is credible and can be
used in the development of forming reasonable grounds or, alternately, they may find that the
credibility of the witness cannot be established, and the evidence cannot be used in the
development of reasonable grounds to take action.
The Truthfully Incorrect Witness
As much as witnesses are a critical component of the criminal investigation process, they can
also become a critical threat to the accuracy and integrity of evidence gathering. This sometimes
occurs in an anomaly where an apparently credible, independent witness tells their version of
events and they are significantly wrong in what they say they observed. Unlike cases where a
witness is motivated to intentionally fabricate or exaggerate their account of events, the truthfully
incorrect witness has no malicious intent and will provide their version of the events with a
genuine belief that what they are saying is true and accurate. This type of witness is an
independent observer with no motivation to lie, and as such the weight of their testimony can
carry significant influence for the investigator’s reasonable grounds to believe and eventually
carry significant probative value for proof beyond a reasonable doubt in the court. For
investigators, the truthfully incorrect witness can become a paradox capable of misleading the
outcome of the investigation resulting in a guilty suspect going free or an innocent suspect being
arrested and charged. This anomaly of truthfully incorrect witnesses is an issue that investigators
must remain mindful of. Witnesses are human and humans are fallible. Even for a witness who
appears to be independent and credible, there remains a need to scrutinize and fact check the
witness’s version of events against the known physical evidence and the accounts of other
witnesses.
The importance of the investigator being mindful of a truthfully incorrect witness cannot be
emphasized too strongly. In 1996, for example, the National Institute of Justice in the United
States released a report concerning the implications of eyewitness testimony and false memories,
and in it, reported that 90% of all DNA exoneration cases defendants were wrongly convicted
upon the false memories of eyewitnesses (Brainerd, 2005). More recently, Smarlarz and Wells
(2015), citing The Innocence Project, noted that eye-witness testimony was used to convict
innocent people in over 70% of DNA exoneration cases. More recently yet, Rose and Beck
(2016) note that eyewitness testimony accounts for more wrongful convictions than anything
else. Research has shown that false memories in eye witnesses can be created in a number of
ways, including through leading questions, reports from others, contact with other people,
suggestions, a witness’ own expectations, the expectations of others, other social pressures, and
media (Bennett, 2015; Allen, 1991). It has also been established that witness recall can be
affected by stress (Morgan et al, 2004) and by alcohol (Oorsouw et al, 2015) in complicated
ways.
Dominant Witness Influence and Conformity
One of the negative dynamics that can occur in an investigation where there are multiple
witnesses is the contamination or influence of witness statements by a dominant witness. This
influence can occur when witnesses to an event have not been separated before any interactions
or conversations have occurred between the witnesses. These dynamics are possible in almost all
cases, and an investigator must always be mindful that this potential exists. It is also possible that
a dominant witness will boldly and sometimes aggressively state their version of the events,
which can cause other less confident or less sophisticated witnesses to question their own
perspective. In such cases, a less dominant witness may change their version of the events or
even omit observations to conform to what the dominant witness stated.
Most susceptible to this kind of influence are very young witnesses, elderly witnesses, or
witnesses who have timid personalities. On some occasions, where there is an imbalance of
power or status in a personal relationship, or even in a subordinate organizational relationship,
witnesses may conform to the more powerful witness out of fear of repercussions or hope of
favour. In some cases, the dominant witness has a vested interest in having their version of the
events stated their way, and the dominant influence towards the other witnesses is intentional and
implicitly threatening in its tone.
In cases where witnesses have interacted prior to being interviewed, each witness should be
interviewed in seclusion from the others. Witnesses should be asked if they have discussed the
event with anyone else or heard anyone else’s version of what happened. They should be
cautioned and encouraged to disregard anyone else’s version of events and limit their version to
their own account of what was seen and heard during the event.
Uncooperative Witnesses
One of the many unpleasant dynamics of criminal activity is when the police attend the scene of
a crime and witnesses, or even victims, refuse to cooperate with investigators. Sometimes, these
uncooperative persons are part of the criminal lifestyle and are not willing or interested in
cooperating in the justice system. The only strategy for police in these cases is to gather as much
forensic evidence as possible in relation to the event and to seek charges where sufficient
evidence can be found.
Although these uncooperative witnesses may believe they are not required to participate in the
criminal justice system, it is entirely possible to subpoena an apparent witness to attend court to
be questioned regarding the criminal event they witnessed. If that witness refuses to answer
questions in court, it is possible for the judge to find them in contempt of the court and to
sentence them accordingly.
Dostal, P. (2012). Conspiracy (Offence). Retrieved January 15, 2017, from The Canadian
Criminal Law Notebook: http://criminalnotebook.ca/index.php/Conspiracy_(Offence)
Dostal, P. (2012). Counselling. Retrieved January 15, 2017, from The Canadian Criminal Law
Notebook:
http://criminalnotebook.ca/index.php/Counselling
Dostal, P. (2012). Informer Privilege. Retrieved January 16, 2017, from The Canadian Criminal
Law Notebook:
http://criminalnotebook.ca/index.php/Informer_Privilege
Dostal, P. (2012). Parties to an Offence. Retrieved January 15, 2017, from The Canadian
Criminal Law Notebook:
http://criminalnotebook.ca/index.php/Parties_to_an_Offence
Dostal, P. (2012). Principled Exception to Hearsay. Retrieved January 12, 2017, from The
Canadian Criminal Law Notebook:
http://criminalnotebook.ca/index.php/Principled_Exception_to_Hearsay
Dostal, P. (2012). Principles of Fundamental Justice. Retrieved January 20, 2017, from The
Canadian Criminal Law Notebook:
http://criminalnotebook.ca/index.php/Principles_of_Fundamental_Justice
Elsevier, B. (2016). Coup contrecoup injury. Retrieved January 27, 2017, from Science
Direct:
http://www.sciencedirect.com/topics/page/Coup_contrecoup_injury
Advamag, Inc. (2017). Rigor Mortis and Other Postmortem Changes. Retrieved January 16,
2017, from Encyclopedia of Death and Dying: http://www.deathreference.com/Py-Se/Rigor-
Mortis-and-Other-Postmortem-Changes.html
EnkiVillage. (2017). How Long Does It Take for a Body to Decompose? Retrieved January 16,
2017, from EnkiVillage: http://www.enkivillage.com/how-long-does-it-take-for-a-body-to-
decompose.html#affix-section-3
Fookes, S. A. (1973). Patrol Sergeant. (A. GEHL, Interviewer)
Gaytmenn, R. S. D. (2003). Quantification of forensic DNA from various regions of human
teeth. Journal of Forensic Science, 48(3), 622-625.
Gecker, R. A. (1989). The Doctrine of Necessity and Its Parameters. Marquette Law Review, 1 –
39 Volume 73 Article 1.
Giannelli, P. C. (2007). Faculty Publications Paper 153. Retrieved Janauary 27, 2017, from Case
Western University School of Law:
http://scholarlycommons.law.case.edu/faculty_publications/153
Gibson, D. (2014). The Kennedy Assassination Cover-up. New York City, NY: Kroshka Books .
Goff, L. (2015). Early post-mortem changes and stages of decomposition. Retrieved from
www.academia.dk Springer Science+Business Media B.V. 2009:
www.academia.dk/BiologiskAntropologi/…/post-mortem-changes.pdf
Government of British Columbia. (2015, Nov 27). British Columbia Police Act. Retrieved from
www.qp.gov.bc.c:
http://www.qp.gov.bc.ca/police/ec36700.htm#34
