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Federal Evidence • Opinion Testimony
EVID#101
Legal Definition
A lay opinion must be rationally based on a witness' perception, helpful to a clear understanding of their testimony, and not based on scientific, technical, or other specialized knowledge.
Plain English Explanation
In court cases, sometimes regular people, not experts, are asked to give their opinion. This is called a "lay opinion." The law says that their opinion can only be based on what they personally saw or experienced. It's like if you saw a car speeding and then crashing, you could say, "That car was going really fast," because you saw it yourself. In contrast, it would be inappropriate for a lay witness to say something like, "Based on my calculations, the car was going 96.5 mph." This rule is there to make sure that people don't guess or use technical knowledge they don't have. It helps keep the trial fair and focused on the real evidence.
Hypothetical
Hypo 1: Bob and Sam are neighbors. One day, Bob's dog escapes and Sam sees it running around. In court, Sam says, "I saw Bob's dog running loose outside." Result: Sam's statement is a lay opinion. He's just describing what he personally saw, which helps to show that the dog was not under control.
Hypo 2: Bob is involved in a car accident with Sam. In court, Bob claims the accident wasn't his fault. Sam, who has no mechanical expertise, testifies that Bob's brakes sounded old and rusty. Result: Sam's opinion about the condition of Bob's brakes is not admissible because it requires mechanical expertise that Sam doesn't have. This is an example of when a lay opinion rule does not apply. In contrast, Sam could have testified that he heard the car making a loud squealing and screeching sound as he observed Bob coming to a stop.
Hypo 3: In a lawsuit, Bob claims his back was injured at Sam's store. Sam testifies, "Bob seemed fine when he left my store." Result: Sam's observation is a lay opinion. He's not a doctor but is just describing how Bob appeared to him, which is relevant to Bob's injury claim.
Hypo 2: Bob is involved in a car accident with Sam. In court, Bob claims the accident wasn't his fault. Sam, who has no mechanical expertise, testifies that Bob's brakes sounded old and rusty. Result: Sam's opinion about the condition of Bob's brakes is not admissible because it requires mechanical expertise that Sam doesn't have. This is an example of when a lay opinion rule does not apply. In contrast, Sam could have testified that he heard the car making a loud squealing and screeching sound as he observed Bob coming to a stop.
Hypo 3: In a lawsuit, Bob claims his back was injured at Sam's store. Sam testifies, "Bob seemed fine when he left my store." Result: Sam's observation is a lay opinion. He's not a doctor but is just describing how Bob appeared to him, which is relevant to Bob's injury claim.
