A prosecutor said in a memorandum Wednesday the decision not to charge Irvin, 43, was due to a lack of available medical evidence as well as inconsistencies in details about the alleged rape of Nicole A. Mostafa July 4, 2007, The Miami Herald said Thursday.
Prosecutors said details of the alleged rape obtained from Mostafa were inconsistent with details obtained from other individuals.
Mostafa alleges she was also forced to perform oral sex on an unidentified man in the alleged incident.
Earlier this month, Mostafa filed a civil suit against Irvin in Broward County Circuit Court stemming from the alleged incident at the Seminole Hard Rock Hotel & Casino in Hollywood, Fla.
An attorney representing the former Dallas Cowboys wide receiver filed a civil lawsuit against Mostafa, seeking $100 million for her alleged attempt to damage Irvin's career and reputation.
Irvin ended his career with the Cowboys in 1999 and currently serves as an analyst for the NFL Network.