The suspect asked for his lawyer several times, each time being "delayed." Everything he said past that point, including the shock of seeing a former victim, the videotaped confession, all of it, would have been inadmissible as evidence against him.
Joe lectures Caitlin that all year long he told his soccer team the final score and winning doesn't matter, that fair play and sportsmanship is what is important, yet earlier in the episode when Caitlin asked him to coach her team and Joe found it her team was the one opposing him, he gloated about how he was going to train them just well enough to not beat his team.