Therefore they have had to search about for a possible motive.

"What possible motive would she have for killing her own son?"

Having found such a person, we must check up on the points of time, place, opportunity, and possible motive.

We have people running down the victim's family, friends, other possible motives.

You never asked who they might be or what their possible motive was.

Police did not give any details about a possible motive.

But the police said they had no information on any possible motive.

The police said they had no information about a possible motive for the killing.

As a matter of fact there was a possible motive.

But he said that was just one of several possible motives.