JANESVILLE, Wis. -- The latest twist in last month's triple homicide at a Janesville mobile-home park has left some neighbors with new fears a killer might still be on the loose, but others said they're still confident the right man is in custody.

The Rock County Sheriff's Department said James Koepp, 48, is still their sole suspect, but recently detectives have been gathering DNA samples from every male resident in the mobile-home park.

Rock County Sheriff Robert Spoden said the voluntary collection is a "pretty standard" investigation practice and that it doesn't indicate they're looking for additional murder suspects.

Still, some lawyers said the size of the sampling sweep is surprising, and they suggested that people seek legal advice before voluntarily giving DNA samples.

Technicians extract DNA, a person's unique genetic fingerprint, and it's often used to help convict criminals.

But dozens of men and boys in the mobile-home park who weren't arrested or charged with a crime voluntarily turned over their DNA to investigators.

Resident Jody Jones said that his three sons -- ages 4, 5, and 8 -- gave DNA samples. Jones said a detective showed up twice at his door, once last Friday and again last Monday, and that the detective wanted to swab his cheeks and his boys'.

"I said fine, you know, go ahead. I have nothing to hide and when they came back to do the boys -- the boys have really nothing to hide. The boys got swabbed, and I got swabbed and since then, that's all we really heard."

Some of the men who gave voluntary DNA samples said the detectives who came to their homes made them feel "comfortable." They also said they want to do whatever they can to aid in the investigation of the Lentz family slayings. Danyetta and her teenage daughter and son were all found killed in their home on Jan. 12.

About 40 men and boys living near the victims' home have voluntarily turned over their DNA to authorities the last couple of weeks, WISC-TV reported.

The sheriff said that investigators want to identify and eliminate any DNA at the murder scene that might have come from people who visited the Lentz mobile home.

Madison civil rights attorney Jeff Scott Olson said he understands their motive.

"If you can explain away all the DNA at the scene from neighbors who were visitors, it helps construct a neater case," Olson said.

Despite that, Olson said he advises against submitting a voluntary DNA sample for three reasons:

"No. 1: The police have the legal right to lie to you. No. 2: They obviously don't have enough evidence to charge anybody yet, so they're still looking. And No. 3: They don't always get the right person in these murder investigations."

Olson said people should first consult an attorney before turning over a DNA sample. He said that if someone has given a sample already and signed some sort of release, that person and a lawyer should read the document and follow up on any promises it contains relating to DNA disposal.

Officials with the state Department of Justice, which oversees the state Crime Lab, said that only convicted felons and unknown perpetrators are entered into its offender computer database. The lab said it will not retain records of anyone else's DNA on any computers.

DNA material will be returned to the Rock County sheriff after testing, WISC-TV reported.