He has an ironclad/perfect 'alibi'. [=an alibi that cannot be proved false]
Her doctor is her 'alibi': she was in surgery at the time of the murder.
Nobody could confirm his 'alibi' that he was at the movies.
(..) They've probably fired me already. The basic rule here is that people hold on to their jobs as long as they show up. If I had to verify every alibi, I'd never get out of the office. But she's been suffering from an illness. Depression. Depression is just self-pity mixed with laziness. (..)2015 Virgin Mountain