Trusted (In) Him

[CaseyA]

June 2, 2002 - Joni Cesta - Dedicated Caregiver - Profile - NYTimes.com

It was in his eyes all along, she had said, and she trusted in him despite signs to the contrary. "Not too many people would do that," he said.

http://www.nytimes.com/2011/01/09/opinion/09rich.html

Even in post-shellacking mid-December, polls found that Americans still trusted him more than Washington’s Republican leaders to fix the nation’s ills — health care included, according to the ABC News-Washington Post survey on that question.

What is the difference between "trust in someone" and "trust someone"?

[Rover_KE]

There's usually very little difference.

You can read more opinions here.

Rover

[CaseyA]

So "trust someone" is informal?

[bhaisahab]

So "trust someone" is informal?

No, it's neither formal nor informal.