Leon Walker, 33, faces a charge of felony misuse of a computer under a state hacking law after he read Clara Walker's e-mails without her permission on a laptop in their Rochester Hills home in 2009.
If convicted, he could face up to five years in prison. Walker's trial date is set for April 11.
It's a case that could set bold new boundaries in the murky area of privacy between a husband and a wife.
In a December interview with "Nightline's" Bill Weir, Walker's ex-wife fired back at what she said were sympathetic portrayals of her ex.
"He violated my privacy. I was violated," said Clara Walker. "It's all about him right now ... because he's making it all about him. He forgot what he did.
Leon Walker, who is Clara Walker's third husband, said he logged into her Gmail account last summer because he was worried about how his wife's affair with another man -- who became her second husband -- was affecting their daughter.
Clara Walker also has a son with her first husband.
"I knew she was involving her son in her relationship. And I was very concerned that she was also doing the same thing with our daughter," Leon Walker told "Nightline."
This is Michigan's first criminal prosecution for snooping through a spouse's e-mails. So far, two Michigan judges have refused to toss out the potentially precedent-setting case.
"It's outrageous. It's insane," Leon Walker told ABC News.
Walker, 33, said it was easy for him to log in because his wife kept the password in a book next to the computer -- something that Clara Walker denied.
Prosecutors contend that Walker -- who is a computer technician -- illegally hacked into his wife's computer after she had filed for divorce, but Walker's lawyer called the prosecution's claim an overzealous application of a law meant to protect trade secrets and credit card data.
"People who live under the same roof, be they married or not, and who share a computer -- as in this instance -- may have some personal privacy lines that they adhere to. And if they don't, that's between the two individuals," defense attorney Leon Weiss said.
"The word 'e-mail' does not appear in this statute. This is an anti-hacking statute," Weiss said. "It does not, in any way, shape or form encompass reading somebody's e-mail."
Prosecutors scoff at defense claims that Walker is a victim.
"Apparently, they are trying the case in the media, because they are not doing so well in the courts," Oakland County prosecutor Jessica Cooper said in a statement.
While Walker's case is a first for Michigan, it is not the first time the privacy between a husband and wife has become a matter for the courts. Some legal analysts said federal privacy laws can be understood to mean that even with a shared computer, password protected e-mail accounts are private, unless one of the parties allows access.
"The law is a simple unauthorized access law: It prohibits unauthorized viewing of someone else's password-protected files," said Orin Kerr, an Internet legal expert.
And experts said the same law could theoretically apply to other forms of communication, including a letter addressed to your spouse.
"If you give them permission, you can do anything you want to. But if you don't, it might be a crime," said Perry Aftab, a privacy lawyer.
Walker will face trial Feb. 14.