The New York architect facing murder charges in a string of deaths known as the Gilgo Beach killings was charged on Tuesday in the death of a seventh woman.Rex Heuermann was charged with killing Valerie Mack, whose remains were first found on Long Island in 2000. Mack, 24, had been working as an escort in Philadelphia and was last seen by her family that year in New Jersey.Macks partial skeletal remains were first found in Manorville, New York, in 2000, about 50 miles (80 kilometers) east of where more of her remains were discovered on Gilgo Beach more than 10 years later. They were unidentified until genetic testing revealed her identity in 2020.Human hair found with Macks remains was sent for testing earlier this year and found to be a likely match with the genetic profile of Heuermanns daughter, prosecutors said in court papers. His daughter is not accused of any wrongdoing and would have been three or four years old when Mack died.RELATED STORY | Florida woman convicted in suitcase murder trial sentenced to life in prisonAppearing on Tuesday in a courtroom in Riverhead, New York, Heuermann told the judge: Im not guilty of any of these charges, your honor.The Suffolk County District Attorneys Office was expected to hold a news conference alongside local and state law enforcement following the court appearance.Heuermann is charged with killing six other women whose remains were found on Long Island.The investigation into the Gilgo Beach killings dates back to 2010, when police searching for a missing woman found 10 sets of human remains in the scrub along a barrier island parkway, prompting fears of a serial killer.Over the years, investigators used DNA analysis and other clues to identify the victims, many of whom were sex workers. In some cases, they connected them to remains found elsewhere on Long Island years earlier. Police also began reexamining other unsolved killings of women found dead on Long Island.RELATED STORY | Murder, other violent crime rates dropped across US last year, new FBI data showsThe case has dragged on through five police commissioners, more than 1,000 tips and doubts about whether there was a serial killer at all.Heuermann, who lived with his wife and two children in Massapequa Park on Long Island and commuted to a Manhattan architecture office, was arrested on July 13, 2023, and charged with murdering Amber Lynn Costello, Megan Waterman and Melissa Barthelemy. He was charged in the deaths of three other women Maureen Brainard-Barnes, Sandra Costilla and Jessica Taylor earlier this year. He has pleaded not guilty to all charges.In a June court filing, prosecutors said they had recovered a file on a hard drive in Heuermanns basement that he used to methodically blueprint his killings including checklists with tasks to tick off before, during and afterwards, as well as lessons for next time.In court papers on Tuesday, prosecutors said the document, which was created the same year as Macks murder, includes details that align with her case.For example, it names Mill Road a road near where Macks first remains were found under the heading DS, which investigators believe stands for dump site.The document also lists foam drain cleaner under Supplies. Prosecutors say that on Oct. 3, 2000, Heuermanns phone records appear to show him making two calls to a Long Island plumbing company, and he paid another company the following month to check his mainline drain.In recent searches of Heuermanns home and office, authorities say they found old magazines and newspapers with articles about the Gilgo Beach killings and investigation that prosecutors believe he kept as souvenirs or mementos. Among them was a July 29, 2003 copy of the New York Post that included an article about the disappearance and deaths of Mack and Taylor.Prosecutors are also looking into the death of Karen Vergata, whose remains were first discovered in 1996 and finally identified in 2022 after a new DNA analysis.In September, authorities released new renderings of an unidentified victim who was found in 2011. Officials said the victim, who for years they had identified as male, may have presented outwardly as female and died in 2006.