Denis Michael McDowell Sr., 62, of Mount Airy, the director of technical services for the Philadelphia District Attorney's Office who helped crack cases as a a video-surveillance expert, died of brain cancer Thursday at home.
"Denis was the go-to guy for radios, beepers, cell phones, cameras, computers - any kind of technical gadgets," District Attorney Lynne M. Abraham said. "He was so helpful to young lawyers who needed technical assistance in court as well as to investigators in the field."
One of the more dramatic cases Mr. McDowell helped solve was the slaying of Trish McDermott, 25, an X-ray technician who was shot and killed May 17, 2005, just after getting off a SEPTA bus to go to work at Pennsylvania Hospital.
By piecing together snippets from area security-camera tapes and improving the resolution of the photos, Mr. McDowell and his team were able to isolate video showing a man walking up to McDermott, shooting her in the back of the head, and then running away.
He and his staff studied 200 hours of videotape from the cameras to extract 10 to 15 minutes of relevant film. "You're looking at an hour's worth of video to try to pick up three seconds," he told a reporter at the time. Because the images are so fleeting, he said, "if you don't take your time, it's very easily missed. That's why you have to keep going back and forth."
Police used the edited tape to conduct a manhunt that led to the arrest of Juan Covington, who in 2006 pleaded guilty to McDermott's killing and two others. He was sentenced to three life terms.
Mr. McDowell, who was diagnosed with brain cancer more than three years ago, worked until November while undergoing aggressive chemotherapy and radiation therapy. "He was "extraordinarily brave and determined," Abraham said.
Before joining the District Attorney's Office in 1989, Mr. McDowell had been a detective with the electronic-surveillance unit of the New Jersey State Police.
He was well known in his field and published articles in electronics journals, his son Christopher said. He was proud to be a civil servant, his son said.
A native of Teaneck, N.J., and a U.S. Air Force veteran, Mr. McDowell had a television-repair service in Matawan, N.J., before joining the New Jersey State Police in 1979.
There wasn't anything he couldn't fix, from cars to home appliances, his son said. "He was a jack-of-all-trades and master of all," he said.
Mr. McDowell enjoyed reading U.S. and military history and visiting historic sites, especially in Washington. He preferred vacations in cold-weather areas, such as Newfoundland, loved spending time with family and friends, and made root-beer floats with his grandchildren.
In addition to his son Christopher, he is survived by his wife of 43 years, Judy Wittmann; sons Denis Jr., Andrew, and Carl; a daughter, Kerrith; a brother; a sister; and eight grandchildren.
A Funeral Mass will be offered at 11 a.m. today at St. Madeleine Sophie Roman Catholic Church, 6440 Greene St., Philadelphia. Friends may call at 9 a.m.
Donations may be made to Face to Face Foundation, 109 W. Price St., Philadelphia 19144.