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.

The tone in the dozens of e-mails between the two was sometimes quite familiar, according to the person who has read them. Dookhan opened up about her life, confiding in one ­e-mail that she was unhappy in her marriage, though it is unclear from a printout of the e-mails whether she sent it. On another occasion, Papachristos reminded her that their relationship was strictly “professional” in ­response to something Dookhan wrote.

The correspondence, which dates back to 2009, was unusual enough that State Police inves­tigating drug lab misconduct recently interviewed ­Papachristos about their relationship. Lab protocol calls for prosecutors to communicate through lab supervisors to avoid any question about the integrity of drug evidence, something Dookhan has acknowledged she should have done.

The American Civil Liberties Union has asked Attorney General Martha Coakley and the district attorneys to agree to throw out all drug cases “involving a police officer or prosecutor who, at any time, communicated directly with Annie Dookhan.”

“Chemists aren’t supposed to be doing favors on a case-by-case basis for a particular police officer or prosecutor,” said ­Matthew R. Segal, legal director of the ACLU Foundation of Massachusetts. “That’s a good rule, no matter who the chemist is.”

Dookhan wrote e-mails and spoke on the phone with other prosecutors, the person ­involved with the investigation said, but the correspondence with Papachristos stood out.

Papachristos declined to ­answer questions, but his boss, Norfolk District Attorney ­Michael W. Morrissey, said ­Papachristos told him that he and Dookhan had no personal relationship.

“George never socially met her or had a relationship with her,” said Morrissey, who took office in 2011. “He met her once in court, and she never testified in any of his cases.”

However, Morrissey admitted that he has seen only a few e-mails, and he has refused ­repeated efforts by investigators to provide him with copies of the rest of the correspondence, because they are “the subject of an ongoing investigation” by Coakley and “I don’t want to interfere.”

Several state officials and prosecutors expressed confusion over Morrissey’s refusal to accept the e-mails, noting that he should know if one of his subordinates had an inappropriate relationship that could jeopardize cases in his office.

Morrissey also declined to give the Globe the handful of Dookhan-Papachristos e-mails in his possession on the grounds that the case is under investigation.

Dookhan analyzed drug evidence for numerous cases in Norfolk Superior Court in ­Dedham where Papachristos was assigned, including an Oxycodone-­dealing conviction obtained by Papachristos that was one of the first to be overturned after allegations against Dookhan became public. It is unclear exactly how frequently Dookhan analyzed evidence for Papachristos, but Papachristos refers to several different cases in his e-mails.

Dookhan’s lawyer, Nicolas Gordon, declined to comment, saying he had not seen the ­e-mails.

As much as anything, the ­e-mails may offer insight into the mind of Dookhan, who has admitted to State Police that she falsified and mishandled drug evidence, potentially jeopardizing up to 34,000 drug cases she took part in during her nine-year career at the Jamaica Plain lab. She faces criminal charges on accusations of stating that a drug sample contained cocaine when it did not, resulting in the defendant’s conviction. She is also accused of falsely claiming she had a master’s degree in chemistry.

Many have wondered what would possess the bright, hardworking 34-year-old mother of a young son to behave so recklessly.