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January 17, 2019

Lesson Two: Weighing in on the evidence

Lesson Description
In this lesson students individually and in small groups rank different types of evidence for its reliability and importance to jurors.  Students then reconsider rankings after exposure to brain research studies.

Students will be able to:

  • understand the role jurors play in evaluating evidence.
  • describe the differences between reliable and less reliable evidence used in court trials.

C3 Framework for Social Studies Standards
D2.Civ.2.6-8. Explain specific roles played by citizens (such as voters, jurors, taxpayers, members of the armed forces, petitioners, protesters, and office-holders).

GRADES:  9-12

DURATION:  One class period

MATERIALS:  Survey handout, Class chart, Brain research studies described in Insight articles


1.  Introduction:  As a citizen you may be summoned to serve on a criminal jury. Your duty is to determine if the defendant is guilty or not guilty.  The prosecution must prove the defendant is guilty beyond a reasonable doubt.  At the trial many different types of evidence will be presented through witness testimony.  During jury deliberations, you will consider how important each piece of evidence is in deciding guilt.  Today’s lesson asks you to examine more closely the importance of different types of evidence.

2.  Ask students to rank different types of evidence on a survey.
 SURVEY:  Which type of evidence presented at trial is most valuable in determining whether a defendant is responsible for a crime?  Rank each type of evidence from 1 (MOST RELIABLE) to 10 (LEAST RELIABLE)
_____ expert testimony
_____ police investigator
_____ fingerprint evidence
_____ DNA testing
_____ eyewitness testimony
_____ video of the scene
_____ lie-detector test
_____ photograph of the scene
_____ confession
_____ bite marks
2.  Divide class into small groups and:

  • compare survey rankings 1-3 and 8-10
  • reach a consensus on top 3 and bottom 3, be prepared to explain your choices
  • on class chart record a + (plus) under Most Reliable column for each of your top 3 most reliable types of evidence and record a – (minus) under Least Reliable column for each of your 3 least reliable types of evidence
  • total the marks on each evidence line in both columns
  • Which types of evidence do we rank as most reliable? least reliable?

Types of evidence

Most Reliable (1-3)
Grp 1   Grp 2   Grp 3   Grp 4   Grp 5   Grp 6   Total

Least Reliable (8-10)
Grp 1   Grp 2   Grp 3   Grp 4   Grp 5   Grp 6   Total

expert testimony



police investigator



fingerprint evidence



DNA testing



eyewitness testimony



video of the scene



lie-detector test



photograph of the scene






bite marks



3.  Ask class:

  • Looking at our most reliable types of evidence, what do they have in common?  How are they different from our least reliable types of evidence?
  • What factors make evidence more reliable?  less reliable? 
  • What questions do you have about any of these types of evidence?   What information do you need to know about evidence presented in court?


4.  What does psychology and brain research tell us about certain types of evidence?  In this issue of Insights, authors refer to brain research studies and its impact on courtroom evidence.  Two studies are summarized below.  In pairs, read each summary and discuss how this new information affects your rankings.  Then re-evaluate your rankings for eyewitness testimony and confessions.  Did you make changes?  Explain.

Memory research and eyewitness testimony by victim
How accurate is human memory when confronted with a realistic and personally relevant threat?  A series of experiments were conducted with elite military personnel undergoing military survival school training.  Participants endured physical aggression and intimidation tactics during a mock interrogation such as being physically struck and stared down.  Cortisol levels during this phase of training were equivalent to jumping out of an airplane for the first time.  Despite the elite training of these military individuals, approximately two-thirds of participants later misidentified their interrogator in a line up even though they had a clear view of their interrogator’s face for 30-40 minutes.
Source:  Study cited in article working title, “The reliability of eyewitness testimony:  What psychological research tells us about the limitations of memory.”

Research on videotaped confessions
How accurate are videotaped confessions by the defendant? In a series of experiments led by the psychologist G. Daniel Lassiter of Ohio University, mock juries were shown exactly the same interrogation, but some saw only the defendant, while others had a wider-angle view that included the interrogator.  When the interrogator isn’t shown on camera, jurors are significantly less likely to find an interrogation coercive, and more likely to believe in the truth and accuracy of the confession that they hear – even when the interrogator explicitly threatens the defendant.

Source:  Can a Jury Believe What it Sees?  Videotaped Confessions Can Be Misleading by Jennifer L. Mnookin, July 13, 2014

Extension Activity

Ask students to explore Insights articles for other research examples and explain how it connects to different types of evidence.      

5.  Conclusion:  What does research tell us about evidence?  What role does a juror play in evaluating evidence?  Summarize today’s activity by identifying 3 key tips jurors should remember when weighing evidence.