CHICAGO (WGN) -- A mother from Chicago has been waiting nearly 40 years for answers about her son.
Michael Marino is listed as one of the 33 victims of John Wayne Gacy, but his mother, Sherry Marino, always had her doubts.
She had his body exhumed in 2011 for DNA tests.
The DNA test came back and showed the body is not that of her son Michael, which means there may be another unidentified Gacy victim.
See images from the case:
John Wayne Gacy
After 40 years, DNA results show Michael Marino is not Gacy victim
FILE PHOTO -- This is John Wayne Gacy's police arrest photo from Dec. 21, 1978. Following intensive research, investigation and surveillance, Gacy was arrested by the Des Plaines (Ill.) Police Department on Thursday, Dec. 21, 1978. After being charged with and serving time for 33 murders, Gacy was executed in 1994 by lethal injection. Today, Monday, Nov. 23, 1998, technicians began preliminary work on a possible excavation at an apartment building on Chicago's Northwest Side in search of as many as four more possible victims of the mass murderer. The apartment building at one time, was the home of Gacy's mother, and Gacy had done some construction work there. The information regarding the location was recently released from a retired Chicago police officer who said he had seen Gacy carrying a shovel near the area at about 3 a.m. one day in 1975. The former officer reportedly thought little of the Gacy sighting until three years later, when Gacy was charged with 33 murders. The apartment building is about four miles away from Gacy's house. (Des Plaines Police Department, Tim Boyle)
The grave of an unidentified victim of John Wayne Gacy is seen at Woodlawn Memorial Park in Forest Park, Illinois, on Wednesday, October 12, 2011. The Cook County Sheriff's Department exhumed eight bodies in the hopes of identifying the victims. (Keri Wiginton/Chicago Tribune/MCT via Getty Images)
CHICAGO, IL - NOVEMBER 23: Chicago Police and hired technicians use a ground penetrating radar device in an attempt to confirm the existence of more bodies, victims of serial killer John Wayne Gacie, 23 November. Authorities are expected to dig the parking lot in the coming days at the apartment building where Gacy's mother lived. The investigation began when press reports quoted a retired Chicago detective as saying that in 1975 he witnessed Gacy carrying a shovel outside the building in the middle of the night. (Photo credit should read JAY CRIHFIELD/AFP/Getty Images)
Behind this apartment building on Chicago's northwest side, photographed on Monday, Nov. 16, 1998, Chicago police may dig in search of as many as six more victims of mass murderer John Wayne Gacy. The possible burial site was found by ground-penetrating radar after information was released recently from a retired Chicago police officer that he had seen Gacy carrying a shovel near the area at about 3 a.m. one day in 1975. The former officer reportedly thought little of the Gacy sighting until three years later, when Gacy was charged with 33 murders. The apartment building is about four miles away from Gacy's house where 29 bodies were found in 1978, 27 in the crawl space and two in the yard. Chicago police are now waiting for the owner of the property to cooperate with the issued search warrant to dig up the area. Gacy was executed by lethal injection in Ill., in 1994. (Photo/Tim Boyle)
Sheriff Thomas J. Dart announces the identify of one John Wayne Gacy's unknown victims during a press conference at the Daley Center in Chicago, Illinois, Tuesday, November 29, 2011. The victim, William George Bundy, who went missing in October of 1976, was 18 years old. Bundy had been working construction jobs for Gacy. (Cook County Sheriff/Chicago Tribune/MCT via Getty Images)
Cook County Sheriff's office officials examine containers that hold the upper and lower jaws and their teeth of the unidentified victims of John Wayne Gacy in June 2011. They were stored for many years at the county's medical examiner's office and in 2009 were buried in a paupers' grave. After the Cook County Sheriff's office obtained a court order, a wooden box containing eight smaller containers shaped like buckets, each holding a victim's jaw bones and teeth was dug up at Homewood Memorial Gardens in June 2011. (Cook County Sheriff's office/Chicago Tribune/MCT via Getty Images)
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Michael was 14 when he disappeared in October of 1976.
His mom always doubted he was in Gacy's crawlspace, or buried underneath the tombstone bearing her son's name.
However there was a possibility that Marino's body had been switched with another Gacy victim, Kenneth Parker, who was a friend of Michael's.
Attorney Steve Becker wants the Cook County Sheriff's Department to respond. They will enter Michael's name in a missing person's database, and will contact Sheriff Dart to let him know that after 40 years, there may be another unidentified victim of John Wayne Gacy.