It depends on the situation. I have been approached by cops twice--and had no problem with talking to them.
The first case involved a detective investigating an accusation by someone we knew against someone else we knew. There was no suggestion we were anything but observers, no reason not to talk.
The second time was out at a trailhead, I had just finished a hike. They were working with search & rescue extracting someone who broke a bone. They correctly deduced where I had been and came over and asked about the snow conditions high on the mountain. In hindsight I was a little annoyed at how they asked it as I responded a bit too literally--addressing the snow conditions but forgetting the three trees that had fallen across the trail, one of which would have been a substantial obstacle to a stretcher evacuation.
The first case involved a detective investigating an accusation by someone we knew against someone else we knew. There was no suggestion we were anything but observers, no reason not to talk.
The second time was out at a trailhead, I had just finished a hike. They were working with search & rescue extracting someone who broke a bone. They correctly deduced where I had been and came over and asked about the snow conditions high on the mountain. In hindsight I was a little annoyed at how they asked it as I responded a bit too literally--addressing the snow conditions but forgetting the three trees that had fallen across the trail, one of which would have been a substantial obstacle to a stretcher evacuation.