They're sold to the highest bidder - artwork, letters, even murder weapons from America's most notorious killers.
The collectibles have been coined "murderabilia" and it is big business for some.
Single pieces are bought and sold on the murder market for thousands of dollars, but it's so controversial the sales are banned from eBay.
Just the word "serial killer" gets some kind of reaction out of most, but for some, expressionless faces and the dark stories behind them has become an addiction. Collector William Harder told FOX Carolina he can't get enough of prying into the minds of killers.
"First time I saw a drawing by a serial killer I just wanted to have it, so I wrote that offender and started visiting him," said Harder.
Now Harder often visits local prisons, befriending even the most notorious villains, like Charles Manson. He runs murderauction.com and said buying and selling crime memorabilia should be considered a hobby.
The highest-dollar item from South Carolina on the site now is a sketch belonging to notorious serial killer Donald "Pee Wee"' Gaskins. Gaskins was convicted of killing 10 people. He later claimed in an autobiography he'd killed more than a hundred individuals.
Former solicitor Dick Harpootlian was the prosecutor for Gaskins' final case, and knew him well.
"He was very smart, very crafty and very evil," said Harpootlian.
Harpootlian said he visited Gaskins often in his prison cell. He even got a look at the convicted killer's artwork.
"The cell was underground, brick, and Pee Wee was down there, and he showed me his drawings he was doing at the time," said Harpootlian. "Of course, I didn't think they were very good."
But Harpootlian has something that would be considered gold on the murder market, a piece of twisted and burnt metal from a homemade bomb Gaskins used to blow up a fellow inmate. It was his final murder before he was sentenced to death.
"That would be in the thousands," said Harder. "Something like that, it's a one of a kind. It's extremely historical. It's basically a murder weapon."
So we asked Harpootlian the big question, would he sell it?
"Thousands of dollars? Wow! If someone wants to buy this piece of metal that Pee Wee blew him up with … call me," said Harpootlian with a chuckle.
Harpootlian said he doesn't get the appeal.
"You buy letters like Shakespeare or Einstein. Those are people who have created something wonderful or added to our society," said Harpootlian. "This guy was just a redneck from Florence. I don't know there's anything to admire about him."
Some victim advocates have asked what people admire about individuals convicted of murder, expressing outrage about murderabilia. They also wonder whether the money is landing back in the hands of criminals.
Harder said his site is strictly collectors' only. Not even a penny goes to the killers.
"Inmates probably hate Murder Auction more than the victims' families. Its not the way the victims are saying," said Harder.
But Union County Solicitor Kevin Brackett said that's hard to believe.
"Does the money somehow make it back to them? Do people pay them for this stuff in exchange for profit? I think it would be very hard to trace," said Brackett.
Kevin Brackett has prosecuted several killers in South Carolina, and was even on the team that convicted Susan Smith, the Upstate woman who killed her one- and three-year-old sons. He's not happy letters from Smith are popular on Murder Auction, bringing in $50 a pop.
"I think it speaks more about the person interested in having something like that. What is somebody's fascination with someone who would kill their own children? Why should they deserve any kind of special attention?" said Brackett.
Brackett said just seeing Susan Smith items on Murder Auction is enough for him to support any constitutional legislation that would outlaw murderabilia.
"Things that belonged or had something to do with them, why should that have any special value to anybody? It shouldn't," said Brackett. "The only thing they should be famous for is the terrible thing they did, and that's the only thing people should remember."
Harder said there are some things he has banned from the site, like dirt from victim's graves, items relating to the 9/11 attacks and photos of children.
At this time, there are some victim advocacy groups pushing for legislation for murderabilia sites to be shut down for good.
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