The science teacher at Jefferson High School is murdered on the first day of the academic year. The police narrow down the suspects to four members of the school – the gardener, the coach, the math teacher, and the principal. However, they all have alibis: The gardener says he was trimming the bushes
The coach says he was playing basketball
The math teacher says he was conducting a mid-year test
The principal says he was in a meeting

The police had no trouble in arresting the person guilty of the crime. Who do you think was the murderer?​