A bit of grave digging.

[Xyteno Sane]

In act 3 behind the temple and the circus there's a place to dig up in which there's only a coffin with a person in it. We can't seem to be able to loot the corpse so I was wondering if there's a point to the corpse or if it's just a dead body with nothing special Quest related or anything.

[Raelic]

If you're trying to pick up the corpse and it doesn't work it's because you have too much in your bags already.

You should be able to pick up the corpse or "loot" it. Then drop it on the ground and cast talk with dead on it.

But it's not really necessary, there's a ton of ways to get answers. That's just one. You can convince the nurse inside too. And cast talk with dead there. It all leads to the same thing.

[Kittybass]

It is quest related. You have to start the Investigate The Murders quest at the temple. I think you have to break the casket open and use the spell to talk to the dead, but you have to get the quest at the temple first, start talking to NPCs and they start giving you clues.