He played college football for the California Golden Bears, and was recognized as a consensus All-American.

In his senior year with the Golden Bears, O'Neal set the NCAA single-season record of four interceptions returned for touchdowns and was recognized as a consensus first-team All-American.

In the 2005 season, O'Neal recorded ten interceptions, breaking the franchise record of nine, set by Ken Riley in 1976 and equalling Ty Law as the NFL's interception leader that year.

[5] O'Neal signed with the Houston Texans on August 6, 2009, following an injury to cornerback Jacques Reeves.

On December 9, 2006, O'Neal was arrested in the Pierce Twp community of Cincinnati after he was pulled over for driving while intoxicated.

In December 2019, O'Neal was charged with one count of DUI with serious injury and one of DUI with property damage in Royal Palm Beach, Florida after speeding 100 mph in his Mercedes Benz and striking a utility pole, causing the vehicle to catch fire on August 7, 2019.