rescue tests and the location of her head wound. conrad's lawyers were ready to argue that heidy took her own life. but a witness who knew her as long as anybody would tell a different tale. with the conclusion of our story, here's josh mankiewicz. >> conrad truman had been convicted of murder, sentenced to life and had already served more than three years. now, the revelation of those flawed police measurements had led to conrad truman's new trial. that stunned everyone in the utah county d.a.'s office. especially the man responsible for conrad's conviction, prosecutor craig johnson. >> this is something that really took us by surprise. >> reporter: the defense says you had to have known. >> well, that's their take, and they're doing their job to zealously represent their client, but i can tell you categorically that that's not correct. >> reporter: just as stunned was the man whose team took the measurements, lead detective tom wallace. what went wrong? how'd that happen?