The investigation took approximately six weeks, during which state and federal authorities reviewed millions of documents and public records in their attempt to locate the identity of Weinberger's kidnapper.

The investigation led to the arrest of then-31-year-old Angelo John LaMarca, who eventually confessed to kidnapping and abandoning Peter Weinberger due to mounting debts and financial difficulties.

During his highly-publicized trial in Nassau County, New York, LaMarca attempted to attribute the murder to a state of temporary insanity caused by stress around his financial problems.

[5] The documents filed in relation to LaMarca's probationary period would play a significant role in his capture for the Weinberger kidnapping.

On July 4, when Peter was 32 days old,[7] his mother, Betty Weinberger, placed him in a carriage covered with mosquito netting on the patio of their house in Westbury, New York,[8] a town in Nassau County, and left him unattended for approximately 10 minutes.

She returned to find that someone had pulled open the netting, taken Peter, and left a ransom note on notebook paper in green ink.

Betty Weinberger's husband Morris, a wholesale pharmacist,[9] soon returned from a car ride with their older son, two-year-old Lewis, at which point the two called Nassau police.

Meanwhile, police requested that the local press refrain from reporting on the story for 24 hours to reduce the risk of the kidnapper harming Peter.

Nevertheless, the New York Daily News reported on the kidnapping that same evening and drew copious amounts of attention to the event.

[11][6] The next morning, a swarm of reporters and photographers had descended upon the drop-off point, likely deterring the kidnapper from returning to retrieve the money.

One hoax caller lured Betty Weinberger to a movie theater and used the opportunity to steal her purse.

[9] On August 22, 1956,[10] six weeks after the kidnapping and after the FBI had analyzed over 2 million public records in an attempt to find a handwriting match,[6][11] a federal probation officer in Brooklyn, New York, found a document in his files with handwriting that matched the unique writing style of the ransom notes' author.

The defendant in that case was then-31-year-old Angelo LaMarca, who had been convicted of bootlegging[6] in Suffolk and had just completed his term of probation.

After FBI handwriting experts concluded that LaMarca had written the ransom notes, Nassau County police planned the arrest in a way that was intended to avoid harm to Peter Weinberger if he were still alive.

[6] When asked for a motive, LaMarca said that he was $1,800 in debt after buying a refrigerator and storm windows for his house and that he was behind on his car payments.

Nassau County's medical examiner later testified during LaMarca's trial that Peter may have lived for about one week before dying.

In an unusual twist, Nassau County District Attorney Frank Gulotta decided to prosecute the case himself.

[14][15] LaMarca's defense at his trial was that he was driven to temporary insanity due to his mounting debts and that he was otherwise a normal, hardworking husband and father of two.

Reporters who witnessed LaMarca's testimony remarked that he sounded "often hazy and uncertain" and gave confusing responses to some of his defense attorney's questions under direct examination.

[17] LaMarca's wife Donna testified that she noticed a shift in his behavior after he purchased the $15,000 house at which he was arrested.

The defense's final witness was a psychiatrist, Dr. Thomas S. Cusack, who testified that LaMarca was insane both during the kidnapping and when he later abandoned Weinberger.

[19] The prosecution called another psychiatrist, Dr. Ernani D'Angelo, to rebut Dr. Cusack's testimony and LaMarca's contention of insanity.

[12] On August 6, 1958, one of LaMarca's attorneys, Nancy Carley, attempted to obtain a writ of habeas corpus to stay her client's execution, which was scheduled to take place the next day.

Carley argued that Judge Mario Pittoni had refused to answer a question from the jury and had thus denied LaMarca a fair trial.

Afterwards, Carley stated that no other legal action in the case was likely and that LaMarca's only chance of survival was if New York Governor W. Averell Harriman agreed to grant executive clemency.

"[23] Governor Harriman's office received 400-500 telegrams from people opposed to LaMarca's execution, but he refused to intervene.

[22] Until the end of LaMarca's life, Donna insisted that he was insane, stating to a reporter after making her radio appeal, "I just can't believe my husband will die.

[24][25] His last meal had consisted of fried chicken, French-fried potatoes, vegetables, ice cream, and coffee.

He was not observed to have said anything in the death chamber except quiet muttered responses to the chaplain's prayers, and one comment to a guard placing a strap over his eyes and face: "What are you trying to do, choke me?"

[6] Later, in 1998, the Protection of Children from Sexual Predators Act would allow the FBI to become involved in kidnapping investigations prior to 24 hours passing.