There was a crimes that shook britain episode about Rachel Nickell on crime+investigation just now. I didn’t know much about the original case because I was really young at the time and never really looked into it. The way they implicated that poor man while Napper was still at large was terrible! I didn’t know that he has also raped and murdered another woman and her child. So many duck ups there he could have been caught much sooner.
If you read Paul Britton's book, The Jigsaw Man, you'll understand that there were many reasons to suspect Colin Stagg. Not many people would get an erection when shown a crime scene photograph of a dead woman for example.
Paul Britton was the criminal psychologist who helped devise the "honey trap" at the suggestion of the police and became the fall guy for it all. It's a really interesting read.
He also covers the murders of Samantha & Jasmine Bisset along with the Green Chain rapes, all committed by Robert Napper, the man who murdered Rachel Nickell, which he was involved in as well.
Lots of other crimes are covered in the book too including the murder of James Bulger, Fred & Rose West, Colin Pitchfork (first man convicted using DNA) - all of which he worked with the police on.
I would really recommend it.