Could the pressures of maintaining a double identity have caused an esteemed Boston doctor to bludgeon his wife of 31 years to death?

A jury drawn from the affluent suburbs of Norfolk County, Massachusetts, must decide whether Dr. Dirk Greineder, who lived a secret sex life, killed his 58-year-old wife, Mabel. The doctor and father of three faces life in prison if convicted of first-degree murder.

Friends and family knew Greineder, 60, as a devoted husband and accomplished doctor who lived for more than 20 years in the leafy town of Wellesley.

Mabel "May" Greineder

But sometimes, whether in rented motel rooms or his home office, Greineder revealed a different side of himself, one he called "Thomas Young," the alias the doctor used when cruising the Internet for pornography and during trysts with prostitutes.

With transformation never more than a closed door and a few mouse clicks away, Greineder was able to juggle his secret life and his known persona for many years. But prosecutors say that, just like in Robert Louis Stevenson's classic crime story The Strange Case of Dr. Jekyll and Mr. Hyde, the doctor's secret identity caused him to practice murder as well as medicine.

Dr. Dirk Greineder: A Classic Success Story

Close acquaintances say that violence is out of character for Greineder, a success-oriented man known for his devotion to both family and work.

Dr. Dirk and Mabel Greineder's wedding photo

Born in Germany, Greineder grew up in Lebanon and moved to America to attend college. He received an undergraduate degree from Yale University and then a doctorate in pharmacology from Case Western Reserve University.

Greineder met his wife Mabel in graduate school, while training to be a doctor and she a nurse. The couple was married in 1968 in Cleveland and eventually settled in the Boston area.

The doctor achieved professional success, rising to the position of director of clinical allergy programs at Boston's Brigham and Woman Hospital, a top-ranked medical research facility. He also taught at the Harvard Medical School.

The Greineders during happier times

Mabel "May" Greineder gave up her own career to stay at home and raise three children, Kirsten, now 30, Britt, 28, and Colin, 25. All three have supported their father throughout the case and insist on his innocence.

"I'm feeling outrage and I'm feeling frustration in a system, with a system that I feel has failed us, a system that we attempted to trust in and it has failed miserably with putting on trial and indicting an innocent man," Kirsten Greineder said two days after her father was indicted.

"Mr. Thomas Young": The Darker Side

The Greineder children didn't know about their father's alter ego until details about the case were revealed. Greineder hid his secret life well, allegedly using his second identity to run up $1,100 in phone sex charges, download Internet pornography onto his hard drive, chat online with others interested in his fetishes, and arrange meetings with prostitutes.

The Greineder children have publicly supported their father's claims of innocence

"Loved your pics! Looks like you are into some [bondage and domination] too," the doctor allegedly e-mailed one woman he met online. "I have some interest/experience with this though I have given up all of my toys. Maybe you still have some! But mostly, I liked the images and I am sure that I will love to play with you."

Elizabeth Porter, a prostitute who says Greineder paid her for sex on two occasions, testified during grand jury proceedings that the doctor rented a room in the Westin Hotel in Boston and bought champagne, roses and "a lot of expensive stuff." He then paid her $450 for 90 minutes in which they had sex and Greineder watched her take a shower.

Using the alias Thomas Young allowed Greineder to remain anonymous during these encounters, but the doctor also seems to have attached special significance to the name. In his days at Yale, he had a classmate named Thomas Young, who lived a far different lifestyle than the bookish Greineder.

"I always liked him a lot," said the real Thomas Young when contacted by The Boston Herald after Greineder was arrested. "His study habits and mine, I ruefully confess, were not identical. I wandered around other guys' rooms hoisting brews. He studied a lot."

Halloween Morning

On the morning of Oct. 31, 1999, Dirk and Mabel Greineder went for a walk with their dog in a wooded area near Morse's Pond, where they reportedly used to take their children to swim.

At 8:56 a.m., police received a frantic call from Greineder on his cellphone. The doctor said his wife had been attacked and was likely dead, and requested immediate assistance.

When authorities arrived on the scene, they found Greineder in a wooded area standing over the dead body of his wife, blood smudges on his yellow windbreaker, black jeans and eyeglasses. Mabel Greineder had wounds to her head, neck and chest. Drag marks led from the body to a path puddled with her blood.

The crime scene

Police canvassed the area, collecting evidence, interviewing neighbors and searching for suspects, but the officers believed they already had their killer — Dirk Greineder.

"We were looking at him from the beginning because of the circumstances of the crime scene," Norfolk County District Attorney William Keating told The Metro West Daily News.

Police reportedly collected a bloody glove, a knife, a hammer and several other items near the crime scene. Prosecutors say that DNA evidence from the glove and knife link Greineder to the crime.

The Prosecution's Case

Prosecutors will try to convince jurors that Greineder murdered his wife so that he could more freely indulge his obsessions with pornography and illicit sex.

Greineder is led away in handcuffs following his March 2000 arrest

Keating has hinted that Mabel Greineder may have discovered her husband's infidelity, but says there was friction between the couple nevertheless. "There was an obvious strain in the relationship," the prosecutor told the Daily News.

To prove that turmoil, prosecutors will only be allowed to present Greineder's covert sexual activities within a week of his wife's death. Norfolk County Superior Court Judge Paul Chernoff ruled that the doctor's earlier dalliances, such as those with Bishop, were irrelevant and inadmissible.

But the bulk of the prosecution's case will be physical evidence collected at the crime scene and testimony from witnesses who interacted with Greineder on the morning of the killing.

The Defense's Case

Greineder says that Mabel injured her back on their walk and decided to turn back early, agreeing to meet him at the parking lot where they had left their car. Returning a little later, he says he found her body, checked her pulse, and ran to call for help.

Greineder defense lawyer Martin Murphy contends that police failed to investigate adequately whether Mabel Greineder's killing was the work of a local serial killer. There have been two other murders of elderly people in Norfolk County parks in recent years.

But Judge Chernoff ruled that Murphy may not present a serial killer theory to the jury, although he will be allowed to question police witnesses about the other two killings.

"The fact that two murders occurred within the same county is simply irrelevant," the judge wrote in a ruling just before jury selection. "Norfolk County is merely a geographically disparate subdivision, and crime knows no boundaries."

The defense is expected to stress Greineder's reputation as a quiet and trustworthy man, and minimize his activities as Thomas Young as unrelated to the case.

Opening arguments are expected to begin Thursday. Before the jury hears them, however, the judge plans to take them on a trip to the crime scene.