< Go rent A CRY IN THE DARK, one of the best movies about this kind of things ever made. >
A similar movie to watch that shows just how police tactics can comepletely screw up an investigation and actually get an innocent person to admit to a crime they didn't commit, try "A Death in Canaan". I used to think it was impossible for people to admit to a murder they didn't commit...then I read about this case and saw the movie.
Don't get me wrong, I think this is a rare and extreme case and in almost every case I think it's rectified, as it was in "Canaan". Police need some leverage.
Here's a blurb of the movie:
"A Death in Canaan is an utterly brilliant film based on the real-life murder mystery of teenager Peter Reilly,accused of the brutal murder of his own mother.Paul Clemens stars as the accused young man in question,and the entire cast of this 1978 made -for television film features allstars. Stephanie Powers,Brian Dennehy,and the late Kenneth McMillan lead the way in this outstanding masterpiece.The film takes the viewer on all the twists and turns of the trials,and the ending is perfectly done and intensifies the mystery,which to date remains unsolved."
It's actually rather common. People just get tired and tell the questioners what they want to hear.