Ajiboye Arrested for Purchasing Arbitrarily Demonized Pain Reliever

So it turns out that DT Ladi Ajiboye's suspension from the USC football team was in response to a February arrest for allegedly participating in a drug deal.

According to the incident report, shortly after midnight on Feb. 21 at the intersection of Harden and Lady streets, investigators witnessed Ajiboye engage in a “hand-to-hand transaction” with another person. The other person was not identified in the report.

After Ajiboye returned to a car driven by USC offensive lineman Terrence Campbell, sheriff’s personnel followed the 2004 Ford Crown Victoria and pulled it over after Campbell failed to signal for a turn, authorities said.

They found evidence of marijuana use and five grams of pot between the two front seats, which Ajiboye admitted belonged to him, the report stated.

“Our narcotic agents witnessed a drug transaction,” sheriff’s department spokesman Chris Cowan said. “They saw him get into the car. They made the stop. He was arrested.”

I'm a little confused about the sequence of events here. Why was the arrest made after the failure to singal instead of after the transaction was witnessed by the narcotis agent?

Maybe one of our law students could shed some light on this?