Dr. Henry Peter Ackerman

Dr. Henry Peter Ackerman (Baltimore County Police)

The 13-year-old case of a missing Baltimore County doctor was solved Tuesday, with a surprise murder confession announced in a federal courtroom nearly a thousand miles away.

Dr. Henry Peter Ackerman was a 48-year-old widower and recent transplant to the Baltimore area when he went missing in the summer of 1998 during a trip to Memphis, Tenn. He and his wife, Velma, had lived in a suburb there before her death from leukemia in 1994, and Ackerman went back to the area planning to buy a vehicle and drive it to his new home in Maryland, federal prosecutors said.

But he never returned, and more than a decade would pass before anyone looked to Dale Mardis, a gun dealer, for answers.

Mardis, 57, was convicted earlier this year in federal court in Tennessee in the racially motivated killing of an African-American code enforcement officer named Mickey Wright in 2001. Mardis shot Wright, dismembered the body with a Becker BK-1 Brute survival knife, burned it and spread the remains in junk cars that were later crushed, according to court documents and news accounts.

The extreme nature of the crime prevented Wright's family from being able to bury "their beloved," prosecutors noted in a sentencing memorandum. What they didn't know until last week was that it wasn't the first time Mardis had set a man on fire to conceal a killing.

A witness who came forward last month told prosecutors that Mardis might have killed a Maryland man, the U.S. attorney for the Western district of Tennessee, Edward L. Stanton III, said in a telephone interview.

Investigators reached out to Ackerman's sister and to Baltimore County police, who had a full file on Ackerman that showed many hours' work, Stanton said.

Baltimore County Police Spokeswoman Cathleen Batton provided a 1992 photo of Ackerman to The Sun from his missing person file, showing the doctor in graduation garb after completing a doctorate program at Memphis University. He wears a cap and glasses and a sober expression along with his long hair.

Batton said Ackerman, who was living on the 6700 block of Maple Leaf court, just north of the city/county line, was reported missing June 26, 1998.

Mardis filled in the rest of the story.

Ackerman had met Mardis at a gun show and eventually struck up enough of a friendship that the doctor made plans to visit the dealer while on his trip. They got into an argument over a debt, Mardis said, and he bludgeoned Ackerman with a hammer, then disposed of the body by burning it.

Stanton credited the confession to the "relentless efforts" of Memphis prosecutors and FBI investigators. This is a "group of folks that would not stop with investigating this case until the end, until literally the days before" sentencing, Stanton said.

Lawyers kept the development secret until Tuesday, when Mardis was scheduled to be sentenced in the Wright killing, though there were hints in a court document filed over the holiday.

Mardis had been pushing back against a pre-sentence report and recommendation that he receive a life term, but his lawyer abruptly dropped those efforts Monday, filing paperwork that said "as a result of circumstances that will be fully explained in open court on July 5th, 2011, the defendant hereby withdraws all objections."

Those circumstances were the confession in the Ackerman case.

Mardis was sentenced to life in federal prison Tuesday in Wright's murder, and he agreed to plead guilty in a Tennessee state court to killing Ackerman and to accept another life sentence for the crime.

Stanton's team told the news to Ackerman's sister, who lives in New Jersey.

"She was overcome with grief, as you can imagine, but at the same time, relief as well just to have the knowledge," Stanton said. He declined to reveal her name.

"Justice delayed is not justice denied," Stanton said. "The sentence that Dale Mardis received today is certainly warranted, and we're hopeful that this begins a chapter of closure" for the families.

An earlier version of this story incorrectly identified the doctor as a city man, due to inaccurate information from Tennessee prosecutors. The Sun regrets the error.

tricia.bishop@baltsun.com