I think something that could be really cool is reading facial expressions. Imagine if you talk to someone and ask a question, the killer in this example, they lie and say they do not. It would be neat to be able to know their expressions like descriptors. Nervous, Sad, Angry, Sleepy, ect.
Some killers may be sloppy and easy to read. Others may be stone cold professionals.
Another example, Maybe someone is helping cover up for a friend's murder. They mislead you, look nervous. So you look through their friends PC thinking they might be the killer. You find an email talking about how the actual killer needs help as they did something bad and to meet up. Now you know who the killer is.
I feel expressions could add a lot to the immersion. You could take this a step further with nervous ticks, maybe able to be read if you get a disk?
