Why don't the police believe Gallien at first when he says he knew the dead hiker?

The police had already received six calls from people claiming to know the Chris' identity. They saw Gallien's call as just another false lead.

“OK, sure,” replied trooper Roger Ellis, the cop on the other end of the line. “What makes you think so? You’re the sixth person in the last hour who’s called to say they know the hiker’s identity.”