Guerin was shot dead while driving her car near Dublin and, the Independent says, Irish police believe Traynor tipped off the gunman who drove up beside her on a motorcycle and killed her.
Traynor was a key figure in the Dublin criminal underworld and was seeking a court order to prevent her from writing about his activities.
Traynor was named in court by underworld associate and drug trafficker John Gilligan as the man who ordered Guerin's murder.