Justice still hasn't been served for the admitted killer of 6-year-old New Yorker Etan Patz.

Pedro Hernandez has already confessed to the 1979 killing of Patz, but on Friday his case was declared a mistrial after a jury failed to reach a verdict following 18 days of deliberation, according to USA Today. Judge Maxwell Wiley told the jury to continuously try to come to a decision, but they approached him three times, saying it was too difficult.

The prosecution has already requested a new trial date.

"We are frustrated and very disappointed the jury has been unable to make a decision. The long ordeal is not over," said Etan Patz's father, Stanley Patz. "I think we have closure already."

Hernandez, who was a stock clerk at a New York City convenience store in 1979, confessed to the murder in 2012 after a tip led police to him. His lawyers say he is mentally ill and that his admission was not genuine though, according to the Associated Press.

The defense believes a different, "longtime suspect" is the real killer.

"I am so convinced Pedro Hernandez kidnapped and killed my son," Stanley Patz said "... His story is simple, and it makes sense."

Police have never found Etan Patz's body or anything he was wearing at the time of his disappearance. The story made national headlines, and his face was one of the first ever featured on the "missing person" portion of a milk carton. Hernandez, according to the prosecution, confessed to multiple people that he is the killer.

Prosecutor Joan Illuzi-Orbon said Hernandez "told police he lured Etan into a bodega basement with the offer a soda, and immediately began choking the child," USA Today reported.

Hernandez will stay in jail as another trial is likely. His lawyer, Harvey Fishbein, agrees with the public that the case, which has been open for 35 years, needs to be closed, but only if the right person is put behind bars.

"I would say there's only a resolution if the correct man is held responsible, and we firmly believe Pedro Hernandez is not the right man," Fishbein said.

District Attorney Cyrus Vance thinks Hernandez is the correct man.

"We believe there is clear and corroborated evidence of the defendant's guilt beyond a reasonable doubt," Vance said. "The challenges in this case were exacerbated by the passage of time, but they should not, and did not, deter us."