"We're always hopeful for that one clue that pushes us over the top, that gets us closer to solving them," he said.
"We have probably interviewed people within all three of those investigations that hold the key to breaking those cases wide open," Knight said.
What is known
The body of Rowland, 43, was found by a jogger on the C&O Canal towpath near Sandy Hook in southern Washington County in the early hours of Nov. 15, 2002.
Knight said police were continuing to withhold Rowland's cause of death, hoping that his killer might slip and reveal the details. Rowland was an elementary school teacher in Jefferson County, W.Va., when he died.
Robinson's live-in girlfriend, Carrie Nicole Simmons, found Robinson's body inside his 10719 Timothy Drive home in Halfway on Oct. 21, 2004, about 10:30 p.m. He had been fatally shot.
Robinson, 28, was a father of four and a former North Hagerstown High School wrestling and football standout.
Gelvin arrived at her 109 Hebb Road home on Jan. 4, 2005, around noon, but before she could go inside, she was pushed down and robbed of her purse, Knight has said. She died at Washington County Hospital on Jan. 13, 2005, the result of complications from a pelvic fracture sustained when she was pushed down, he has said. Medical examiners ruled her death a homicide.
Gelvin, 86, previously owned and operated Gelvin's General Store in Smithsburg and rented property in the Leitersburg area, according to her obituary.
In addition to the unsolved cases, police agencies in Washington County have a combined 10 cases that have gone cold.
"What we consider cold, is when there are no further investigative leads and no one has been charged in that case," Hagerstown Police Department Lt. Mike King said.
The oldest of the 10 cold cases in the county dates to 1975.
Leads on six of the homicides ran out for investigators at the Maryland State Police barracks in Hagerstown. Investigators at the Washington County Sheriff's Department have one cold case, and detectives at the Hagerstown Police Department have three.
Sgt. Otis Whitaker, with the Maryland State Police Cold Case Unit, said Wednesday that he recently reviewed the case file in the April 1984 death of 15-year-old Loraine Zimmerman. He said he expects Zimmerman's death and Goldie Elizabeth Fritz's March 1979 death to be "looked at hard" soon by cold case investigators.
State Police Detective Sgt. John Cook said the two cases have been assigned to two investigators with the homicide unit who worked in the Hagerstown barracks.
Whitaker said that with cold cases, investigators must focus on one case at a time. He said that the unit has focused recent efforts on solving a Cecil County, Md., cold case. He said police got a break in that case, but he could not go into detail about the investigation Wednesday.
King said the Hagerstown Police Department's detectives have been assigned to each of the department's three cold cases in an effort to familiarize them with the circumstances, people and facts in each case.
King said police consider the Valentine's Day 1994 stabbing deaths of Daniel and Wilda Davis at their West Wilson Boulevard home an open investigation. Russell Wayne Wagner was convicted for their murders and died in prison while serving two life sentences.
"It is closed, technically, because there was an arrest in it, but we believe there were others involved," King said Thursday.
City police also consider the June 1986 disappearance of Mark Patrick Wacker an open case. Police have no new clues in his disappearance, but presume that Wacker is dead, King said.
Wacker, 24, who was working at Nova Industries at 2315 Pennsylvania Ave., last was seen at his sister's residence in the first block of Manor Drive on June 20 of that year, City Police Detective Patricia Moulton said Thursday. A missing persons report was filed and entered into a national missing persons database, but no hits were ever made, she said.
Wacker last was seen wearing a button-down shirt, blue jeans and tan suede shoes. His apartment was in order, but police found that his cats had not been attended for several days. His car was parked in an unusual spot, two blocks from his Oak Hill Avenue home, Moulton said.
Detectives were not able to rule out foul play, Moulton said.
Maryland State Police Cpl. T.E. McDonough said Wednesday that police still were investigating the death of a man whose bones were found near Pen Mar in July 2006.
Police preliminarily identified the bones as those of Charles Calvin Lessner, who last was seen by his family more than 20 years ago. Among the remains, police found an identification card for Lessner, who had lived in Cascade, Frederick, Md., and Thurmont, Md. The bones have been sent to a Texas laboratory for DNA testing to confirm his identity, McDonough said.
Because police found only bones, McDonough said, "I'm not sure if it will ever be determined how he died."