Collier was dismissed from the Hurricanes earlier this month, but Kiffin was satisfied the junior deserved a second chance.
"He wanted a fresh start," he said. "If you talk to the people there, including the people extremely high up there, they felt very good about the kid.
"He's been through a lot. He's had a very tough life so far. I'm glad we could give him an opportunity. Talking to a number of people, I think it's very clear that this is something that's very good for him, to get away from home, and start fresh. I know he's excited to be here as well."
In two seasons at Miami, Collier caught 44 passes for 574 yards and three touchdowns. He also scored on two punt returns in 2009.
With the Trojans trying to integrate three freshman receivers into their offense, Collier gives Kiffin a capable veteran to use on the scout team.
Collier will be eligible to play in 2011 after sitting out this season. He could be at practice as early as Monday if cleared.
"He'll play on our service team all year long and get a chance to play for us in the spring and next year," Kiffin said.
Down to just 70 scholarship players, USC has been looking for ways to add players before scholarship reductions take effect.
"When the sanctions first took place and people started attempting to raid our roster, we basically took the approach that we need to research any possible transfers that there are with our numbers where they're at," Kiffin said.
Kiffin even joked that Collier was part of a trade for freshman offensive tackle Seantrel Henderson, who signed with USC but was released from his letter of intent after NCAA sanctions were handed down in the Reggie Bush case.
"A player to be named later, too," Kiffin said.
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