According to the skill descriptions, there is nothing to stop any character from making untrained psynicience skill tests.  Is this correct?

Thaddux said:

I believe you need a Psy rating to use Psyniscience.

Plushy said:

I also believe this to be correct.

Rules-as-written, there is nothing preventing anyone from making an untrained Psyniscience check, but I believe that to be just an oversight. Only psykers should be able to make Psyniscience checks.

But actualy its quite an intresting idea, what about some new talent? 

Grunt: "Wait guys! I have a bad feeling about this. I think there might be some chaos up ahead."

Commisar: "Really? I see some right here." *BLAM!*

There is an Origin Path in RT that gives out Psyniscience without needing the Psyker trait, iirc.

Seeten said:

Yes, it does, and it is absolutely unique because of that. It also mentions that the Inquisition is very keen on learning how exactly they manage to pull it off.

By "Very keen" I assume you mean "Planning to do an autopsy on you while you are still alive".

Just to show the actual RAW on it since it hasn't been referenced, its covered on p.111 under the Psyker trait. You must have the trait to buy psynisciance.

That said, the notion you could use it untrained is hilarious. I always did feel that was one of the failings of letting any non-specialist skill be used untrained.

It could be a result of training and experience. There comes a point where you've been exposed to warp-stuff so often that once in a very big while, you spot it happening or passing by.

Given a 30-40 score at -20, if you realise that guy there's one of those gut-wrench-inducing reality-buggerers one fifth of the time? Not too good for an educated guess, but better than nothing.