Alleged Gilgo Beach serial killer Rex Heuermann contacted dozens of sex workers hundreds of times, prosecutors say

Accused Gilgo Beach serial killer Rex Heuermann allegedly used burner phones to contact dozens of sex workers more than 500 times up until the months before his arrest, according to a new court filing. 

The alleged contacts took place over the course of two years, according to the court filing, which is a prosecution response to defense efforts to suppress evidence.

Search history shows "an absence of mistake," expert says

Heuermann also allegedly conducted thousands of internet searches for "hardcore violent pornography" and "images of bruised and impaled women," along with more than 100 searches about serial killers and the Gilgo investigation itself. 

Prosecutors say it's evidence Heuermann is a sexual sadist. 

Former prosecutor Vinoo Varghese calls it damaging evidence that is likely to be allowed. 

"These show an absence of mistake, that he was using and making these calls, and learning about how to torture people in order to perform these acts upon his victims. So the prosecution's argument is that these are relevant acts," Varghese said. "It is also very likely that the prosecution feels that they have an extremely very strong case and are not offering anything short of life in prison." 

Trial may start after Labor Day

Heuermann is charged with seven murders going back decades. 

In January, the defense filed motions challenging much of the evidence, claiming that a single hair is all that allegedly links Heuermann to victim Sandra Costilla. Prosecutors say the case doesn't rely on a single hair, but rather a pattern across the victims. That pattern, according to prosecutors, includes decades-old articles about the murders he allegedly stored in pristine condition. Prosecutors say they have more than 150 potential witnesses to call when and if the case goes to trial.

The defense has said it is planning for a trial, and not a plea. CBS News New York has reached out to Heuermann's defense attorney for comment on this most recent filing, but we have not yet heard back. 

The judge is set to rule on all issues on March 17, when Heuermann will be back in court. The judge is pressing for a trial right after Labor Day.