A mistaken identity defense is used when a witness incorrectly states that a person was involved in a crime, when they were not.  This defense is often utilized when there is eyewitness testimony and the defendant did not commit the crime.
The New York Court of Appeals, our highest court, in 2017, recognized the unique problems that exist with eyewitness identification between races. As such, any time identification is an issue in a criminal case and the witness and the person charged are different races, you have the right to request the jury be charged about the problems with such identifications.