A New York architect who is already charged with four murders has now been charged with two more deaths.
Rex Heuermann, 60, appeared in court accused of killing Jessica Taylor in 2003 and Sandra Costilla in 1993.
Prosecutors cited DNA evidence and a “blueprint” of the suspected serial killer’s alleged crimes found on a computer.
Since 2010, police have been investigating a string of at least 10 deaths on Gilgo Beach, Long Island.
On Thursday, Mr Heuermann pleaded not guilty to the latest charges.
Suffolk County District Attorney Raymond Tierney told a news conference that officials had found a document they believe the suspect used to “methodically” plan the crimes in “excruciating detail”.
It included columns labelled “problems” and “supplies”. Under the “problems” column, “DNA”, “tire marks” and “blood stains” were among items listed.
Terms like “booties” and “police scanner” were under the “supplies” column, according to court documents.
Police believe two other columns in the file labelled “DS” and “TRG” stood for “dump site” and “targets”.
The planning document found on Mr Heuermann’s computer also breaks down sections into “pre-prep”, “prep” and “post-event”, which prosecutors believe to be a guide to planning the murders, according to court documents.
“Post-event” includes a checklist with items like “change tires”, “burn gloves” and “have story set”.
A section labelled “RECON” details steps to package a body for transport and lists items to dispose of after a murder.
One list labelled “body prep” notes to “remove head and hands”, which was the state of Ms Taylor’s body when police discovered her remains.
Mr Heuermann appeared to make to-do lists for himself, according to court documents. Lists of reminders included “get sleep before hunt” and instructions on how to attack victims quickly and quietly.
Another reminder instructs Mr Heuermann to “use push pins to hang drop clothes from ceiling – not tape”.
The document also includes instructions highlighting lessons from past murders, detailing the best killing methods that Mr Heuermann had researched.
Mr Tierney said investigators had discovered the Microsoft Word document, which was created in 2000, on a laptop.
Mr Heuermann has been held without bail since he was arrested last July outside his Manhattan architecture office.
He was initially charged with the murders of three women: Melissa Barthelemy, 24, Megan Waterman, 22, and Amber Costello, 27.
Investigators filed new charges against him in January for the murder of a fourth woman: Maureen Brainard-Barnes, 25.
The remains of the four, believed to be sex workers, were discovered near Gilgo Beach in 2010.
Investigators seized hundreds of electronic devices from Mr Heuermann’s home that they believe he used to communicate with the women.
These included 27 computers, eight laptops, 15 cameras, 80 hard drives, 46 mobile phones, eight laptops, four GPS devices, nine wifi routers, 17 tablets and 42 USB devices, as well as floppy disks and VHS tapes.
An analysis of those devices found Mr Heuermann had a large collection of violent, bondage and torture pornography and “that material was very similar to the condition that the two latest victims were left in”, said Mr Tierney.
Investigators also found nearly 300 guns in his home.
Mr Tierney said police had discovered Ms Taylor in 2003 decapitated and with her hands and arms severed below the elbows. He added that a tattoo on her body had been obliterated by a sharp object.
Eight years later, her arms and skull were found off Ocean Parkway, in the same location as the four women whom Mr Heuermann was first charged with murdering.
The remains were all found within 50ft (15 metres) of the roadway, Mr Tierney said.
The prosecutor said the body of Ms Costilla was found on 20 November 1993 by two hunters in a wooded area of Southampton, New York.
She had 25 “sharp-force” injuries, which were believed to have been inflicted “post-mortem”, including to her face, torso, breast and genitals, he said.
Officials said DNA tests on male hairs that were found under the body of Ms Taylor and on Ms Costilla’s shirt indicate they came from Mr Heuermann.
Investigators believe Mr Heuermann’s wife and children were out of the state during five of the murders, according to the most recent indictment.
This left the suspect with “unfettered” time to plot his alleged crimes from the family home in the Massapequa Park neighbourhood of Long Island.
Investigators initially accused a carpenter from Manorville, New York, of Ms Costilla’s death, but have since cleared him.
That suspect, however, was convicted of killing two other women.
By BBC News
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