Zarelli appeared to have been cleaned and freshly groomed, with a recent haircut and trimmed fingernails, although he had suffered extensive physical attacks prior to his death, with multiple bruises on his body.

On November 30, 2022, the Philadelphia Police Department announced that detectives had determined the boy's identity using DNA and genealogical databases.

Despite the identification, the exact circumstances leading to his death are uncertain and the case is still considered an open homicide investigation.

On February 25, 1957,[8] Zarelli's body, wrapped in a plaid blanket, was found in the woods off Susquehanna Road in the Fox Chase neighborhood of Philadelphia.

[13][14] The police also distributed a post-mortem photograph of the boy fully dressed and in a seated position, as he may have looked in life, in the hope it might lead to a clue.

[15] On March 21, 2016, the National Center for Missing & Exploited Children released a forensic facial reconstruction of the victim and added him into their database.

In 1960, Remington Bristow, an employee of the medical examiner's office who doggedly pursued the case until his death in 1993, contacted a New Jersey psychic, who told him to look for a house that matched the foster home.

[9][12] In 1998, Philadelphia police lieutenant Tom Augustine, who was in charge of the investigation, and several members of the Vidocq Society (a group of retired policemen and profilers), interviewed the foster father and the stepdaughter (whom he had married).

[22][better source needed] Another theory was brought forward in February 2002 by a woman identified only as Martha, or "M", accusing her mother of acquiring and killing the child.

[24] In 2016, two writers, one from Los Angeles, California (Jim Hoffmann) and the other from New Jersey (Louis Romano), believed they had discovered a potential identity from Memphis, Tennessee, and requested that DNA be compared between the family members and the child.

Local authorities confirmed that they would investigate the lead, but said they would need to do more research on the circumstances surrounding the link to Memphis before comparing DNA.

[25] At a December 2022 press conference, Philadelphia Police Commissioner Outlaw stated that Joseph's death is "still an active homicide investigation and we still need the public's help.

"[26] Law enforcement reported at the same conference that both of Joseph's biological parents are deceased, but the child has living half-siblings.

[21][27] At the same December 2022 press conference, Philadelphia law enforcement stated that Joseph had lived in the area of 61st and Market streets.

"[29] In January 2023, The Philadelphia Inquirer reported that Joseph's biological parents were Augustus John Zarelli, known as "Gus," and Mary Elizabeth (née Abel) Plunkett, known as "Betsy.