The origin of the AIDS virus is uncertain, but there have been widespread allegations that it was developed at an American biological weapons laboratory by genetic modifications of based SIV, a virus found naturally in monkeys. The man who "discovered" HIV personally testified as an expert witness for the defense, claiming that the gang members were all innocent. Expanding on the Israeli connection, conspiracy theorists have noted that, as a demographic group, Jews are naturally resistant to AIDS for medical reasons, and circumcision is known to confer a high level of immunity.