If I were a clever defence lawyer I'd argue it would invalidate any later line-ups. This sounds like a stellar way to destroy a memory of a face.

Each time you show a person a face, you're adding new memory trace that will conflict with the real one. This will reduce the confidence in a later recognition task. You're also re-activating the real trace, allowing it to be disrupted. This would increase the false-positive rate in a line-up.