According to Merriam-Webster, the definition of ‘Alibi’ is ‘the plea of having been at the time of the commission of an act elsewhere than at the place of commission’.
Alibis are getting easier to prove or disprove due to the influx of security cameras. It seems like privacy is going the way of the dodo bird. (My grandkids are no doubt asking ‘what’s a dodo bird’?)
Nowadays, the term alibi is synonymous with an excuse. Defense teams are using it as their defendant’s excuse for doing something wrong. (It was a full moon, I had PMS, I ate Twinkies…)
As a mystery writer, I try to use the term properly in my books. But you have to be careful because it appears that Big Brother is always watching you. An alibi can be broken or upheld with all the world’s technology. Cell phone towers, security footage, dated receipts, Facebook posts all go towards proving or disproving you were (or weren’t) at a particular place on a particular date. Of course, the prosecutor has the burden of proof.