on trial

on trial  {adv.} or  {adj. phr.}

1. For testing or trying out for a time before making a decision.

I was lucky that I had bought the machine on trial because I didn't like it and was able to return it.

Mother bought a new dishwasher on trial and was trying it out before deciding whether to keep it.

2. In a court being tried for a crime before a judge or jury.

John White was on trial for murder.