Topeka ? After a year’s frustration, relatives of a man and woman who were shot to death in a Topeka duplex hope the offer of a $20,000 reward will prompt someone to remember something about the killings.

Police have spent thousands of hours investigating the deaths of Karen Harkness and Michael Sisco, whose bodies were found by Harkness’ parents on the afternoon of July 7, 2002. Each had been shot numerous times with a 9 mm gun while sleeping in Harkness’ southwest Topeka home.

On Sunday, the families of Harkness, 53, and Sisco, 47, announced at a news conference that they have increased their reward for the arrest and conviction of a suspect from $5,000 to $20,000.

“You can’t price a life at $5,000 or $20,000,” said Mike Worswick, brother of Karen Harkness. “We just want to remind people to have their memories jogged so the little pieces can bring this to justice.”

Worsick said Topeka police “are very involved in this. We’re just trying to help the police get a break.”

The families hired an out-of-state private investigator several months ago to work on the case.

“This person can devote additional time tracking down leads and tracking down the gun purchase,” Worswick said.

Police Lt. John Sidwell said last month that police since October had made no further progress in the case since last October, three months after the killings.

Michael Sisco’s siblings — Tim Sisco of Sacramento, Calif., and Cathy Boots of Pittsburgh — traveled to Topeka to take part in Sunday’s news conference.

Tim Sisco said the Harkness and Sisco families had been friends since before the slayings, and they have weekly contact.

“It’s rocked both our families down to the core,” he said.