 Approximately 75,000 defendants are implicated by eyewitnesses in the U.S. every year, but unfortunately, some eyewitnesses make mistakes.

 75% of the first 218 people exonerated on the basis of DNA analysis had been mistakenly identified.  88% of 121 exonerated prisoners wrongly sentenced for rape in were victims of faulty eyewitness testimony.

 To process information about a crime, we must first perceive a stimulus and then retain it in our minds at least momentarily. But failures and errors can emerge at any step along the way.  Steps to be reviewed here: ◦ Perception ◦ Memory (Encoding, Storage, Retrieval)

 Perception ◦ Certain variables can affect how well we take in information.  e.g., Weapon focus effect: If a weapon is present when a crime is committed, we may devote more attention to it than to the facial features or other physical aspects of the person who has the weapon.

 Stages of Memory ◦ Encoding ◦ Storage ◦ Retrieval ◦ The memory of eyewitnesses in each of these three stages will be described.

What can affect encoding (the acquisition of information)? ◦ Stress: Extreme stress usually causes the person to encode the information incompletely or inaccurately ◦ Characteristics of the witness (e.g., visual acuity and hearing ability)

What can affect storage? ◦ Memory fades as the retention interval increases. ◦ Post-event information can alter memory of the event. ◦ Viewing photos of suspects after witnessing a crime can impair an eyewitness’s ability to recognize the perpetrator’s face in a lineup.

What can affect retrieval?  The wording of questions can influence retrieval (e.g., asking “What was the man with the mustache doing with the young boy?” may influence memory of the man)  Unconscious transference: Victims may pick from a lineup someone they’ve seen before but who is not the actual criminal.

 Interviewing Eyewitnesses ◦ Psychologists created the cognitive interview to help police gather information. ◦ In a cognitive interview, the interviewer develops rapport with the witness, asks the witness to provide a narrative account of the event, and then probes for details with specific questions.

 Interviewing Eyewitnesses ◦ The cognitive interview relies on a set of cues for memory retrieval. The interviewer may ask a witness to:  form an image of the situation,  recollect sights, sounds, smells,  physical conditions, and  emotional reactions experienced at the time. Reforming Identification Procedures

 Instructions to Eyewitnesses ◦ An investigator should instruct the witness that the offender may or may not be present (Malpass & Devine, 1981). ◦ Without this instruction, eyewitnesses may assume that their task is to pick someone, so they choose the person who looks most like the perpetrator.

 Behavioral scientists and police use criminal profiling to narrow criminal investigations to suspects who possess certain behavioral and personality features that were revealed by the way the crime was committed.  Most profiling has been for those who commit bizarre or repeated crimes (e.g., rapists, arsonists, sexual homicides & mass and serial murderers).

 Profilers have interviewed those who have committed a specific type of offense in order to learn how they select and approach their victims, how they react to their crimes, what demographic or family characteristics they share, and what personality features might predominate among them.

 Classifying Homicide Offenders: Mass and Serial Murderers ◦ Historically, most homicides were committed by killers who were well acquainted with their victim, had a personal but rational motive, killed once, and were then arrested.

 Classifying Homicide Offenders: Mass and Serial Murderers ◦ In the past two decades, increased attention has been paid to patterns of homicide involving killers who attack multiple victims, sometimes with irrational or bizarre motives, and who are much less likely to be apprehended than in former days. Profiling of Criminal Suspects

 Classifying Homicide Offenders: Mass and Serial Murderers ◦ Two types of multiple homicides have been identified: mass murders and serial murders.  The mass murderer kills four or more victims in one location during a few minutes to several hours.  In almost 80% of mass murders, the assailant knew the victims. Usually the attack was a carefully planned assault.  The typical assailant is killed at the location of the crime, commits suicide, or surrenders to police.

 Classifying Homicide Offenders: Mass and Serial Murderers  Serial murderers kill four or more victims, each on separate occasions.  Serial killers usually select a certain type of victim (usually a stranger) who fulfills a role in the killer’s fantasies. Usually better planned than mass or spree killings.  Serial murderers are difficult to apprehend (e.g., can seem to be normal community members).

 Steps Involved in Criminal Profiling ◦ 1) Profiling inputs. The profiler collects all information available about the crime. ◦ 2) Decision process models. The profiler organizes the input. ◦ 3) Crime assessment. On the basis of the findings in step 2, the profiler attempts to reconstruct the behavior of the offender and the victim.

 Steps Involved in Criminal Profiling ◦ 4) Criminal profile. The profiler formulates an initial description of the most likely suspects. ◦ 5) Investigation. A written report is given to investigators, who concentrate on suspects matching the profile. ◦ 6) Apprehension. Arrest of a suspect allows the profiler to evaluate the validity of the predictions.