In the process of being tested or tried(adjective)
WordNet. Princeton University. 2010.
Use "on trial" in a sentence
"It happened to be the year O. J. Simpson was on trial for murder, 168 people were killed when a federal building in Oklahoma City was destroyed, and everyone was talking about the Unabomber."
"It took putting the Liberty City crew on trial three times to get a jury to convict them."
"“Have you any tangible evidence to suggest that Salvidienus should be put on trial for maiestas?”"