But the Sept. 11 attacks presented a far greater challenge because of the difficulty of gaining hard evidence.

Could not even gain concrete evidence of his existence as more than a legend being used to motivate the criminals.

There, perhaps, would be quickly gained evidence of Sailor's whereabouts.

If you gain sufficient evidence against him, we shall issue a warrant for his arrest!

Perhaps they'd gained evidence of foul play and if so, they would assume that Jerry was the victim.

Over the course of his imprisonment, British authorities were initially unsuccessful in gaining sufficient evidence.

Remarkable too is the fact that both sides used the technique to gain evidence for their respective hypotheses.

It was the first time in the world a remote data intercept had been used to gain evidence for a computer crime prosecution.

In an effort to gain evidence, the police department sent a letter to 200 parents of current and former children at the school.

His job is to gain evidence against them and bring them to justice.