Expert Testimony on Eyewitness Identification
Dr. P is asked to testify as an expert in a criminal trial involving eyewitness identification. The defendant was identified by a witness who viewed a lineup. The defense attorney wants Dr. P to testify about the reliability of eyewitness memory and suggest the identification was flawed. Dr. P has published research on eyewitness memory but has not reviewed the specific lineup procedures in this case. The prosecutor objects, arguing that Dr. P's testimony would invade the province of the jury. The judge asks Dr. P to explain the basis of his opinions.
1. What are the standards for admitting expert testimony, and how should Dr. P respond to the judge's question?
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Under Daubert (or state equivalents), expert testimony must be based on sufficient facts or data, be the product of reliable principles and methods, and the witness must have reliably applied the principles to the facts. Dr. P should explain his qualifications and the general research on eyewitness memory (e.g., estimator variables like lighting, weapon focus, cross-race effect; system variables like lineup instructions, filler selection). However, Dr. P should acknowledge that he has not reviewed the specific lineup in this case. He can testify about general principles but should avoid opining on the ultimate accuracy of the witness's identification. He should not invade the jury's role; he can educate the jury about factors that may affect memory. If asked about the specific case, he should state that he lacks sufficient information to offer an opinion.
2. How should Dr. P handle the prosecutor's objection that his testimony would invade the province of the jury?
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Dr. P should clarify that his role is to provide scientific context, not to tell the jury what to decide. He can explain that research shows certain factors can influence eyewitness accuracy, but the jury must weigh the evidence. He should avoid using language like 'the identification is unreliable' and instead say 'research suggests that under these conditions, accuracy may be compromised.' The judge will decide admissibility. Dr. P should be prepared to cite specific studies and explain how the research is generally accepted in the field. He should also be ready to explain the limitations of the research and how it applies to the case if he has enough information.