A police procedure done in a police station after an arrest. The police line up the suspect along with several other people, reasonably similar to the suspect, and ask a witness or the victim of the crime whether they can identify the person they saw commit the crime. For example, if a suspect is described as a certain ethnicity or characteristic such as being tall, it would be inappropriate to line up the suspect with a group of very short people and whereby the suspect would stand out.
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TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.