I've certainly not yet learnt the skills of observing and making deductions on really er, practiced psychotic individuals and/or serial killers, but for friends... I can tell if there's something wrong under their seemingly joyful visage. Sometimes, i see it blatantly. When you've known someone for a while, you're more finely tuned to their body language, their gestures, the rise and fall of their voice tones, the look in their eyes. These're plenny of tell tale signs. Other times, i sense it in my heart, that something is amiss.
Every now and then with a friend, when the superficiality of the conversation wears off and when the deeper issues start emerging, inside i'd be thinking: Yeah, i knew there was something wrong.
For my Gem, we've had thoroughly uncanny moments when "coincidence" becomes something like of a central theme running in our relationship. At times, i'd get these vibes about certain specific issues. I only bring up what i think is necessary to bring up, while in other cases, he'll talk me about them and i'm thinking and i tell him: Yeah, i had a feeling about that too.
This so called ability just might be borne from the quality of "natural hyper sensitivity" that females have. Teehee.