Normally I would say NO. However once in a blinding blizzard like snow storm buses had stopped running. I passed a man plodding his way through the snow. Went and dropped off a co worker on the way back he was still plodding along and hadn't gotten far. Years ago someone had picked me up in a similar situation. I picked him up. Usually mass murderers are not knee deep walking in snow.
Probably, but I'd keep my eye on them if I did. It'd also depend on the weather, if it's they middle of a blizzard, the chances will go up. Also, it'd depend on the way the look(though that is giving into stereotypes), if they're clean-cut, I'll trust them more. Or if it's a hot chick. Then the chances go up greatly.