Two Main Categories Of Variables That Affect Eyewitness Identification

Eyewitness identification, a cornerstone of the justice system, is surprisingly fallible. Human memory, much like a video recording, isn't perfect. It's susceptible to distortions and influences that can compromise its accuracy. Understanding the variables that impact eyewitness identification is crucial for ensuring fair trials and preventing wrongful convictions. These variables broadly fall into two categories: system variables and estimator variables.

System Variables: Under Control of the Justice System

System variables are factors that are controllable by law enforcement and the legal system during the process of obtaining eyewitness identification. These variables relate to how the identification procedures, such as lineups and photo arrays, are conducted. Because they are within the control of the system, changes and improvements can be implemented to minimize the risk of error.

1. Lineup Construction:

   • Filler Selection: The individuals or photos used as fillers (non-suspects) in a lineup significantly impact the likelihood of a mistaken identification.
     • Similarity to Suspect: Fillers should resemble the eyewitness's description of the suspect but not so closely that they are indistinguishable. If the fillers are too dissimilar, the suspect might stand out, leading to a biased identification.
     • Match-to-Description Strategy: Fillers should match the general description provided by the eyewitness, even if the suspect doesn't perfectly fit that description. This helps to avoid the "relative judgment" problem, where the eyewitness simply picks the person who looks most like the perpetrator compared to the other people in the lineup, regardless of whether that person is actually the perpetrator.
     • Minimum Number of Fillers: A lineup should contain a sufficient number of fillers (typically five or more) to reduce the probability of a chance identification. Fewer fillers increase the odds that the eyewitness will select someone, even if their memory is weak.
   • Suspect Position: The suspect's position in the lineup should be randomized to avoid any bias. If the suspect is always in the same position (e.g., the first or last position), eyewitnesses might unconsciously be more likely to choose that position.
   • Foils as Suspects: A "blank lineup" procedure can be used where the initial lineup contains no suspect. This helps to gauge the eyewitness's propensity to make a false identification. If the eyewitness identifies someone from the blank lineup, it suggests their memory is unreliable.

2. Lineup Presentation:

   • Simultaneous vs. Sequential Presentation:
     • Simultaneous Presentation: All lineup members are presented to the eyewitness at the same time. This method can encourage eyewitnesses to make "relative judgments," comparing lineup members to each other and selecting the one who looks most like their memory of the perpetrator.
     • Sequential Presentation: Lineup members are presented one at a time. The eyewitness makes a decision about each member before seeing the next. This method forces eyewitnesses to compare each lineup member to their memory of the perpetrator, rather than to the other lineup members, which reduces the likelihood of relative judgments and lowers the rate of mistaken identifications. Research generally supports the use of sequential lineups.
   • Instructions to the Eyewitness:
     • Bias-Reducing Instructions: It's crucial to provide clear and unbiased instructions to the eyewitness before they view the lineup. These instructions should include:
       • Stating explicitly that the perpetrator may or may not be present in the lineup. This reduces the pressure on the eyewitness to make an identification and acknowledges that the actual perpetrator might not be included.
       • Emphasizing that the eyewitness should not feel obligated to make a selection. They should be told that it's perfectly acceptable to say that they don't recognize anyone.
       • Advising the eyewitness that the administrator of the lineup does not know who the suspect is. This helps to prevent unintentional cues or biases from the administrator.
   • Administrator Knowledge: The administrator conducting the lineup should be "blind" to the suspect's identity. This means they shouldn't know which person in the lineup is the actual suspect. This prevents the administrator from unintentionally providing cues or feedback to the eyewitness that could influence their decision. This is often referred to as a double-blind procedure.
   • Post-Identification Feedback: Feedback provided to the eyewitness after they have made an identification can significantly distort their memory and inflate their confidence in their identification.
     • Confirming Feedback: Positive feedback ("Good, you got him!") can make the eyewitness feel more confident in their identification, even if it was incorrect. This increased confidence can then influence their testimony at trial, making them appear more credible to the jury.
     • Disconfirming Feedback: Negative feedback ("That's not the guy") can undermine the eyewitness's confidence and lead them to retract their identification, even if it was correct.
     • Neutral Feedback: Even seemingly neutral feedback ("Okay") can have a subtle influence on the eyewitness's confidence. It's best to avoid giving any feedback at all.
   • Recording the Procedure: Video recording the entire lineup procedure, from the initial instructions to the eyewitness's final decision, is essential for transparency and accountability. This allows the courts to review the procedure and determine whether it was conducted fairly and without bias. It also provides a record of the eyewitness's confidence at the time of the identification.

3. Interview Techniques:

   • Cognitive Interview: The cognitive interview is a technique designed to maximize the amount of accurate information obtained from eyewitnesses while minimizing the risk of contamination. It involves using specific strategies to jog the eyewitness's memory, such as:
     • Reinstating the Context: Asking the eyewitness to mentally recreate the environment and their internal state (e.g., feelings, thoughts) at the time of the event.
     • Reporting Everything: Encouraging the eyewitness to report everything they remember, even if it seems irrelevant or trivial.
     • Reporting in Different Orders: Asking the eyewitness to recount the event in different chronological orders (e.g., backwards, from the middle) to disrupt retrieval strategies and access new memories.
     • Changing Perspectives: Asking the eyewitness to describe the event from different viewpoints (e.g., from the perspective of another witness, from the perspective of the perpetrator).
   • Avoiding Leading Questions: Interviewers should avoid asking leading questions that suggest a particular answer or that incorporate information not provided by the eyewitness. Leading questions can distort the eyewitness's memory and lead to inaccurate reports.
   • Minimizing Interruptions: Interviewers should allow the eyewitness to speak freely without interruption, except to clarify points or to guide the narrative. Frequent interruptions can disrupt the eyewitness's thought process and prevent them from recalling important details.

Estimator Variables: Outside Control of the Justice System

Estimator variables are factors that are present at the time of the crime and cannot be controlled by the justice system. These variables relate to the characteristics of the witness, the perpetrator, the event itself, and the environmental conditions. While the legal system cannot change these factors, they can be estimated and taken into account when evaluating the reliability of an eyewitness identification.

1. Witness Characteristics:

   • Stress: High levels of stress can impair memory and reduce the accuracy of eyewitness identifications. The Yerkes-Dodson Law suggests that there's an optimal level of stress for performance; too little or too much stress can hinder cognitive functions. Crimes, especially violent ones, often involve high levels of stress, which can negatively affect an eyewitness's ability to accurately encode and recall details.
   • Age: Age can significantly impact eyewitness accuracy.
     • Children: Children are more susceptible to suggestion and may be less reliable eyewitnesses than adults. They may have difficulty distinguishing between real and imagined events, and they may be more likely to provide inaccurate reports in response to leading questions.
     • Older Adults: Older adults may experience age-related declines in memory and cognitive function, which can also impair their ability to accurately recall details and identify perpetrators.
   • Alcohol and Drug Use: Alcohol and drug use can impair memory and cognitive function, reducing the accuracy of eyewitness identifications. Intoxication can affect attention, perception, and encoding of information, making it more difficult for eyewitnesses to accurately recall events.
   • Expectations: A witness's prior experiences and expectations can unconsciously influence their perception and memory of an event. People tend to see and remember things that are consistent with their beliefs and expectations, a phenomenon known as confirmation bias.
   • Prior Knowledge: What a witness already knows about a person, place, or thing involved in the crime can subtly alter their recollection. If a witness dislikes a particular person, they might be more inclined to identify them as the perpetrator, even if their memory is uncertain.

2. Perpetrator Characteristics:

   • Disguises: Disguises, such as masks, hats, or sunglasses, can make it more difficult for eyewitnesses to accurately identify the perpetrator. Disguises alter the perpetrator's appearance and obscure key facial features, making it harder for eyewitnesses to encode and recall their identity.
   • Facial Distinctiveness: People are better at recognizing faces that are distinctive or unusual. A perpetrator with unremarkable facial features may be more difficult to identify than someone with a more memorable appearance.
   • Race: The cross-race effect (also known as the own-race bias) is the tendency for people to be better at recognizing faces of individuals from their own race than faces of individuals from other races. This effect can significantly impact the accuracy of eyewitness identifications, particularly in cases where the eyewitness and the perpetrator are of different races. Familiarity and experience with faces from different races can mitigate this effect.

3. Event Characteristics:

   • Weapon Focus: The weapon focus effect refers to the tendency for eyewitnesses to focus their attention on a weapon during a crime, rather than on the perpetrator's face or other details. This can occur because the weapon is perceived as a threat, capturing the eyewitness's attention and diverting cognitive resources away from other aspects of the scene.
   • Violence: Violent crimes often involve high levels of stress and arousal, which can impair memory and reduce the accuracy of eyewitness identifications. The emotional intensity of the event can interfere with the encoding and retrieval of information.
   • Event Complexity: Complex or rapidly unfolding events may be more difficult for eyewitnesses to process and remember accurately. The more details there are to attend to, the more likely it is that the eyewitness will miss or misremember some of them.
   • Time Elapsed: The longer the delay between the event and the identification, the more likely it is that the eyewitness's memory will fade or become distorted. Memory decays over time, and intervening experiences can interfere with the original memory, leading to inaccuracies.

4. Environmental Conditions:

   • Lighting: Poor lighting conditions can make it difficult for eyewitnesses to see the perpetrator clearly, reducing the accuracy of their identification. Darkness, shadows, or glare can obscure facial features and make it harder to encode a clear image of the perpetrator.
   • Distance: The greater the distance between the eyewitness and the perpetrator, the more difficult it is to see the perpetrator's face clearly. Distance reduces the level of detail that can be perceived, making it harder to encode a clear image of the perpetrator.
   • Duration: The length of time the eyewitness has to view the perpetrator can affect the accuracy of their identification. A brief glimpse may not be sufficient to encode a clear image of the perpetrator, while a longer exposure provides more opportunity for accurate encoding.

The Interplay of System and Estimator Variables

It's important to recognize that system and estimator variables don't operate in isolation. They can interact with each other to influence the accuracy of eyewitness identifications. For example, high stress (an estimator variable) can make an eyewitness more susceptible to suggestion during a biased lineup procedure (a system variable). Similarly, poor lighting conditions (an estimator variable) can exacerbate the effects of the cross-race effect (another estimator variable).

Implications for the Legal System

Understanding the impact of system and estimator variables on eyewitness identification has significant implications for the legal system.

• Educating Juries: Juries should be educated about the factors that can affect eyewitness accuracy, including both system and estimator variables. This can help them to evaluate the reliability of eyewitness testimony and to avoid placing undue weight on it. Expert testimony from psychologists can be valuable in educating juries about these issues.
• Developing Best Practices: Law enforcement agencies should adopt best practices for conducting lineups and photo arrays, based on the latest research on eyewitness memory. These best practices should include using sequential presentation, providing bias-reducing instructions, and conducting double-blind procedures.
• Reforming Eyewitness Identification Procedures: Many jurisdictions have begun to reform their eyewitness identification procedures to incorporate the recommendations of researchers and experts. These reforms are aimed at reducing the risk of mistaken identifications and improving the fairness of the justice system.
• Corroboration: Eyewitness identification should not be the sole basis for a conviction. Corroborating evidence, such as DNA evidence, fingerprints, or surveillance footage, should be required to support an eyewitness identification.
• Judicial Scrutiny: Judges should carefully scrutinize eyewitness identification evidence before allowing it to be presented to the jury. They should consider the impact of both system and estimator variables on the reliability of the identification and should exclude the evidence if it is deemed to be too unreliable.

Conclusion

Eyewitness identification is a complex and fallible process. By understanding the system and estimator variables that can affect its accuracy, the legal system can take steps to minimize the risk of mistaken identifications and to ensure that innocent people are not wrongly convicted. Continued research and reform are essential to improving the reliability of eyewitness identification and to safeguarding the integrity of the justice system. The pursuit of justice demands a commitment to understanding the intricacies of human memory and its limitations, ensuring that eyewitness testimony is evaluated with a critical and informed perspective.