Michael Harvey 
The Innocence Game [EPUB ebook] 

They”re young, smart, mostly beautiful – graduate students at an elite university who are naive enough to believe they can make a difference. Little did they know the most important lesson they will learn is how to stay alive.
For Ian Joyce and Sarah Gold the first day of class starts like any other. Then a fellow student, Jake Havens, pulls a wrinkled envelope from his jacket. Inside is a blood-stained scrap of shirt from a boy murdered fourteen years ago and an anonymous note taking credit for the killing. The only problem is the man convicted of the murder is already dead.
Suddenly, the class has a new assignment: find the real killer.