Last June, militants with the self-proclaimed Islamic State committed one of the worst atrocities of their sweep through Iraq. As they took control of the city of Tikrit, they killed perhaps as many as 1,700 young men - at least that's the number that the Iraqi authorities put on the massacre of Shiite soldiers, who were then thrown into a mass grave.
Now that ISIS has been forced from the city, forensic teams have moved in to try to uncover the extent of the crime. The BBC's Ian Pannell has watched the teams at work.
- Ian Pannell, correspondent for the BBC. He tweets @BBCiPannell.
This segment aired on April 29, 2015.