Psychology 162: Psychology and the Law
Professor John Wixted
What is forensic psychology?
● Lie detection – is it possible? Are fingerprint experts accurate? Why do people falsely
confess to crimes? Eyewitness identification – is it reliable? Can we predict who will
commit violent behavior? How useful are criminal profiles?
● Courts:
○ Family Court = child custody/abuse evaluations
○ Civil Court = personal lawsuits (injury, sexual harassment, discrimination)
○ Criminal Court = anyone who is on trial for a crime; competency and insanity
evaluations, false confessions, eyewitness identification, predicting violence
● The Innocence Project: help people who have been wrongfully convicted
○ 1989 – first DNA exoneration took place
○ 375 DNA exonerees to date
○ 69% involved eyewitness misidentification (leading cause of wrong convictions)
Death Penalty
What percentage of death row inmates are innocent?
● From the years 1973 through 2004, an estimated 4.1% were innocent (over 10
years, percentage reduced to about 1.6%)
1. Charles Don Flores
a. Tried in Texas 1999 for being an accomplice to the murder of Betty Black
b. Main evidence was a witness who did not recognize him from a lineup, only
identified him w/ certainty at the trial
c. Convicted and sentenced to death (has been on death row for 24 years)
2. Kevin Strickland
a. Murder case of 3 perps and 3 victims 1978
b. 4th victim (Cynthia Douglas) survived and provided written account claiming she
did not identify the “black guy with the shotgun”
c. Her sister contaminated her memory and Kevin unfairly served in jail for 43 years
● In both cases, we must focus on the FIRST (uncontaminated) test!
○ Fact that witnesses did not initially recognize suspects is evidence of innocence
History of Forensic Psychology
● 1843 Daniel M’Naughten found not guilty by reason of insanity
● 1908 Hugo Munsterberg’s “On the Witness Stand” published
○ Student of Wilhelm Wundt; believed psychology should be applied to practical
concerns (legal setting)
○ Eyewitness memory is fallible and subject to change/corruption over time
○ Memory can be contaminated by suggestive questioning
● 1922 William Marston appointed first professor of legal psychology in the US
, ● 1970s Elizabeth Loftus demonstrated the flaws of memory
● 1990s The Innocence Project
10/3/23
Interrogation vs Interview
● Suspect: reasonable suspicion that this person is guilty (not random)
● Interrogation: person being questioned is suspected of committing the crime
○ Goal = establish guilt/innocence; collect a confession
○ Issue – false confessions sometimes occur (children & mentally disabled)
● Interview: questioning a witness of a crime
○ Goal = collect useful info to identify a perp
○ Issue – can be induced to provide false information
Interrogations:
● “Custodial interrogation” = subject is confined to custody (restricted)
● A reasonable person would have felt he/she was not free to leave (not in custody, but
believed to be detained anyway)
● What rights do suspects in custody have?
○ Miranda Rights (Miranda vs Arizona, 1966): right to remain silent, right to an
attorney, right to an appointed attorney, acknowledgement of these rights
○ Goals = prevent police from coercion/false confessions
● Innocent people feel as if they have nothing to hide and will often waive rights
● However, an innocent person can end up making false confessions w/ coercion
○ Police will try to get a confession any way they can, so many lawyers advise you
to remain silent until an attorney is present
● This is why many innocent people confess to crimes they didn’t commit!
Interrogation Tactics:
● Isolating the suspect from family/friends, conducting interrogation in a small private
room, appealing to self-interest, claiming to have evidence against the suspect,
identifying contradictions in the suspect story, etc.
● With a confession, juries tend to reach a guilty verdict (confessions increase guilt verdict)
● Fundamental Attribution Error: tendency to overemphasize dispositional factors
(something about the person) while minimizing situational factors (something about the
situation) to explain an individual’s behavior
○ Ignoring the situational aspects such as coercion
● The Innocence Project highlights the prevalence of wrongful convictions/false
confessions
Experimental Study of False Confessions
● Researchers paired subjects w/ a confederate for a problem-solving study w/ instructions
to work alone on some trials and jointly on others
, ● Guilty condition: confederate sought help on an individual problem (induced subject to
violate experimental rule)
● Innocent condition: confederate did not request help
● Experimenters accused subject of cheating & tried to get the subject to sign an admission
of guilt using coercive tactics
○ Results: using coercive tactics, 45% of innocent subjects confessed
→ Which condition is best? More guilty and innocent confessions? Or neither?
● None of these are the best option. It’s about value trade-off; whichever you pick, one
problem will go down while the other goes up.
● “Hit Rate” = guilty people confessing to being guilty
● “False Alarm Rate” = innocent people falsely confessing to being guilty
○ Not tied together, both separate pieces of information – need BOTH
● Guilty people are more likely to confess (underlying/invisible motivation)
○ Invisible motivation to confess is most important thing to focus on because the
goal is to maximize the motivation of guilty people to confess while
simultaneously minimizing the motivation of innocent people to confess
Receiver Operating Characteristic (ROC)
● a graph showing the performance of a classification model at all classification thresholds.
This curve plots two parameters: True Positive Rate. False Positive Rate.
Sleep Deprivation and False Confessions (2016)
● Conclusions – sleep deprivation increases likelihood of false confessions
○ Sleep deprivation = higher False Alarm Rate (however, based on this info we
cannot determine the effect on the Hit Rate as they are separate)
4 Types of False Confessions
1. Instrumental: given to achieve a goal
2. Authentic: subject truly believes it as the truth
3. Coerced: police are persuasive
4. Voluntary: given with no police interference
● Voluntary false confession = occurs without prompted by the police; can be the result of a
desire for notoriety, attempt to protect real perp, end the interrogation, etc.
○ Ex – John Mark Karr confessed to the murder of JonBenet Ramsey
● Coerced-Authentic false confession
○ Ex – Peter Reilly failed polygraph and was subjected to 8 hours interrogation until
he finally convinced himself he did commit the crime
● Coerced-Instrumental false confession
○ Ex – Micheal Crowe confessed to killing sister; saying things like “I’m only
saying this because it’s what you want to hear”
Professor John Wixted
What is forensic psychology?
● Lie detection – is it possible? Are fingerprint experts accurate? Why do people falsely
confess to crimes? Eyewitness identification – is it reliable? Can we predict who will
commit violent behavior? How useful are criminal profiles?
● Courts:
○ Family Court = child custody/abuse evaluations
○ Civil Court = personal lawsuits (injury, sexual harassment, discrimination)
○ Criminal Court = anyone who is on trial for a crime; competency and insanity
evaluations, false confessions, eyewitness identification, predicting violence
● The Innocence Project: help people who have been wrongfully convicted
○ 1989 – first DNA exoneration took place
○ 375 DNA exonerees to date
○ 69% involved eyewitness misidentification (leading cause of wrong convictions)
Death Penalty
What percentage of death row inmates are innocent?
● From the years 1973 through 2004, an estimated 4.1% were innocent (over 10
years, percentage reduced to about 1.6%)
1. Charles Don Flores
a. Tried in Texas 1999 for being an accomplice to the murder of Betty Black
b. Main evidence was a witness who did not recognize him from a lineup, only
identified him w/ certainty at the trial
c. Convicted and sentenced to death (has been on death row for 24 years)
2. Kevin Strickland
a. Murder case of 3 perps and 3 victims 1978
b. 4th victim (Cynthia Douglas) survived and provided written account claiming she
did not identify the “black guy with the shotgun”
c. Her sister contaminated her memory and Kevin unfairly served in jail for 43 years
● In both cases, we must focus on the FIRST (uncontaminated) test!
○ Fact that witnesses did not initially recognize suspects is evidence of innocence
History of Forensic Psychology
● 1843 Daniel M’Naughten found not guilty by reason of insanity
● 1908 Hugo Munsterberg’s “On the Witness Stand” published
○ Student of Wilhelm Wundt; believed psychology should be applied to practical
concerns (legal setting)
○ Eyewitness memory is fallible and subject to change/corruption over time
○ Memory can be contaminated by suggestive questioning
● 1922 William Marston appointed first professor of legal psychology in the US
, ● 1970s Elizabeth Loftus demonstrated the flaws of memory
● 1990s The Innocence Project
10/3/23
Interrogation vs Interview
● Suspect: reasonable suspicion that this person is guilty (not random)
● Interrogation: person being questioned is suspected of committing the crime
○ Goal = establish guilt/innocence; collect a confession
○ Issue – false confessions sometimes occur (children & mentally disabled)
● Interview: questioning a witness of a crime
○ Goal = collect useful info to identify a perp
○ Issue – can be induced to provide false information
Interrogations:
● “Custodial interrogation” = subject is confined to custody (restricted)
● A reasonable person would have felt he/she was not free to leave (not in custody, but
believed to be detained anyway)
● What rights do suspects in custody have?
○ Miranda Rights (Miranda vs Arizona, 1966): right to remain silent, right to an
attorney, right to an appointed attorney, acknowledgement of these rights
○ Goals = prevent police from coercion/false confessions
● Innocent people feel as if they have nothing to hide and will often waive rights
● However, an innocent person can end up making false confessions w/ coercion
○ Police will try to get a confession any way they can, so many lawyers advise you
to remain silent until an attorney is present
● This is why many innocent people confess to crimes they didn’t commit!
Interrogation Tactics:
● Isolating the suspect from family/friends, conducting interrogation in a small private
room, appealing to self-interest, claiming to have evidence against the suspect,
identifying contradictions in the suspect story, etc.
● With a confession, juries tend to reach a guilty verdict (confessions increase guilt verdict)
● Fundamental Attribution Error: tendency to overemphasize dispositional factors
(something about the person) while minimizing situational factors (something about the
situation) to explain an individual’s behavior
○ Ignoring the situational aspects such as coercion
● The Innocence Project highlights the prevalence of wrongful convictions/false
confessions
Experimental Study of False Confessions
● Researchers paired subjects w/ a confederate for a problem-solving study w/ instructions
to work alone on some trials and jointly on others
, ● Guilty condition: confederate sought help on an individual problem (induced subject to
violate experimental rule)
● Innocent condition: confederate did not request help
● Experimenters accused subject of cheating & tried to get the subject to sign an admission
of guilt using coercive tactics
○ Results: using coercive tactics, 45% of innocent subjects confessed
→ Which condition is best? More guilty and innocent confessions? Or neither?
● None of these are the best option. It’s about value trade-off; whichever you pick, one
problem will go down while the other goes up.
● “Hit Rate” = guilty people confessing to being guilty
● “False Alarm Rate” = innocent people falsely confessing to being guilty
○ Not tied together, both separate pieces of information – need BOTH
● Guilty people are more likely to confess (underlying/invisible motivation)
○ Invisible motivation to confess is most important thing to focus on because the
goal is to maximize the motivation of guilty people to confess while
simultaneously minimizing the motivation of innocent people to confess
Receiver Operating Characteristic (ROC)
● a graph showing the performance of a classification model at all classification thresholds.
This curve plots two parameters: True Positive Rate. False Positive Rate.
Sleep Deprivation and False Confessions (2016)
● Conclusions – sleep deprivation increases likelihood of false confessions
○ Sleep deprivation = higher False Alarm Rate (however, based on this info we
cannot determine the effect on the Hit Rate as they are separate)
4 Types of False Confessions
1. Instrumental: given to achieve a goal
2. Authentic: subject truly believes it as the truth
3. Coerced: police are persuasive
4. Voluntary: given with no police interference
● Voluntary false confession = occurs without prompted by the police; can be the result of a
desire for notoriety, attempt to protect real perp, end the interrogation, etc.
○ Ex – John Mark Karr confessed to the murder of JonBenet Ramsey
● Coerced-Authentic false confession
○ Ex – Peter Reilly failed polygraph and was subjected to 8 hours interrogation until
he finally convinced himself he did commit the crime
● Coerced-Instrumental false confession
○ Ex – Micheal Crowe confessed to killing sister; saying things like “I’m only
saying this because it’s what you want to hear”
