( CNN ) -- A cold case detective working to identify eight bodies found in John Wayne Gacy 's home in 1978 developed a new way to find other possible victims of Chicago 's most notorious serial killer . Gacy , who worked as a contractor and part-time party clown , lured his male victims with promises of construction jobs , drugs , alcohol or money for sex , or by posing as a police officer . He was convicted in 1980 of killing 33 men and boys in the Chicago area between 1972 and 1978 , but investigators always suspected he had more victims than the 28 found in the space beneath his house and in a nearby river . His DNA was never added to the FBI 's national DNA database -- officially called the Combined DNA Index System or CODIS -- because it did n't exist when he was put to death in 1994 . Illinois law did not provide for the DNA of convicted killers not in prison after it was enacted in 2002 to be added . But Cook County , Illinois , sheriff 's detective Jason Moran , who discovered vials of Gacy 's blood in the cold case file a year ago , also found a legal loophole that allowed Gacy 's DNA and that of others to be entered into the database . Man believed to be Gacy victim found alive . Sheriff Tom Dart hopes the new approach will give investigators around the United States another tool to solve their cold cases . `` This has the potential to help bring closure to victims ' families who have gone so long without knowing what happened to their loved ones , '' Dart said . Moran learned that when the state executes an inmate , the coroner lists the manner of death as homicide . The law allows for the DNA of homicide victims to be added to the database , the sheriff said . `` After review , the Illinois State Police Crime Lab deemed this interpretation acceptable and Gacy 's DNA profile was to be obtained and entered in CODIS , '' a news release from the sheriff said . The DNA of two other executed Illinois killers -- Walter Stewart and Durlyn Eddmonds -- have also been added , according to Will County Coroner Patrick O'Neill . The DNA may not have qualified if these men had died of natural causes while waiting on death row , he said . Computers have reported no matches yet for Gacy , O'Neill said . But Moran 's cold case work did lead to one of the eight unidentified bodies being identified a year ago . DNA comparisons on the exhumed body of `` victim No . 19 '' positively identified him as William George Bundy , who was reported missing in October 1976 . Illinois IDs Gacy victim after 3 decades .
A legal loophole allows DNA of executed killers to be added to the Gacy database . An Chicago detective hopes DNA will reveal additional William George Bundy victims . Gacy was convicted in 1994 of killing 33 men and boys in the Illinois area . He was executed in 1994 , before the national DNA database was created .