alibi

The plea or mode of defense under which a person on trial for a crime proves or attempts to prove being in another place when the alleged act was committed.

to set up an alibi

to prove an alibi

An excuse, especially one used to avoid responsibility or blame.

That day in September, I'm sure you can remember / That's when all the stuff hit the fan (the stuff hit the fan) / You told me a lie, and you didn't have an alibi / But baby, yet I still cared

To provide an alibi for.

To provide an excuse for.