Actually, this is kind of classic investigator gamesmanship.
A bank gets robbed. All the circumstantial evidence seems to point to one person. So, the police decide it must be him, and from there spend 100% of their efforts in finding enough evidence to convict him. And they really don’t like this guy, and really want to convict him.
One problem. The man says he has an ironclad alibi. He was in a specific location at that specific time the bank was robbed. All you have to do is ask the person he was with to collaborate his whereabouts.
The police’s solution? Don’t interview the person he was with.
Sound like good police work to you?