The chemist at the center of the state drug lab scandal carried on an unauthorized, sometimes personal, e-mail and phone correspondence with a prosecutor whose drug evidence she analyzed, a violation of office protocol that may give defense attorneys even more ammunition to throw out drug convictions involving Annie Dookhan’s work.

Though State Police have concluded that Dookhan was not romantically involved with Norfolk Assistant District Attorney George ­Papachristos, Dookhan’s husband was suspicious. At one point, Dookhan’s husband tried repeatedly to contact a startled Papachristos, according to someone involved in the investigation, apparently out of concern that the two were having an affair.