Eyewitnesses to crimes sometimes search for a culprit on social media before viewing a police lineup, but it is not known whether this affects subsequent lineup identification accuracy. The present online study was conducted to address this. Two hundred and eighty-five participants viewed a mock crime video, and after a 15–20 min delay either viewed a mock social media site including the culprit, viewed a mock social media site including a lookalike, or completed a filler task. A week later, participants (...) made an identification from a photo lineup. It was predicted that searching for a culprit on social media containing the lookalike would reduce lineup identification accuracy. There was a significant association between social media exposure and lineup accuracy for the Target Present lineup, but for the Target Absent lineup there was no significant association with lineup identification accuracy. The results suggest that if an eyewitness sees a lookalike when conducting a self-directed search on social media, they are less likely to subsequently identify the culprit in the formal ID procedure. (shrink)