Body of 19th century serial killer HH Holmes exhumed near Philadelphia

Two portraits of American pharmacist and convicted serial killer Herman Webster Mudgett aka HH Holmes. Photo/Getty Images

The body of America's first serial killer is being exhumed in suburban Philadelphia to dispel centuries-old rumours that he conned his way out of his execution and escaped prison.

Dr Henry H Holmes, an infamous killer and conman in Chicago in the 19th century, was hanged on May 7, 1896 in Philadelphia after a life of horrific crimes.

His great-great-grandchildren have now been granted permission by a Delaware County judge to dig up the wealthy, well-educated killer's remains, according to the Daily Mail.

Holmes, who was born Herman Webster Mudgett in 1861 in New Hampshire, was widely rumoured to have killed about 200 people. He once confessed to killing 27.

He moved to Chicago in 1886 after graduating from the University of Michigan Medical School. Holmes began working at a pharmacy in the area but eventually took over the business when the original owner died and his wife mysteriously disappeared.

He purchased a vacant lot of land across from the drugstore and started constructing what eventually became his three-story hotel of horrors.

When the murder castle was completed in 1891, Holmes placed lodging ads in newspapers to draw in unsuspecting women to stay with him.

Guests and employees were required to have life insurance policies and most were never seen again once they entered the hotel.

View of the World's Fair Hotel also known as as the Hotel of Horrors. Photo / Getty Images

The boarding house was designed with about 100 windowless and sound-proof rooms. They had gas lines so Holmes could easily asphyxiate guests and body chutes so he could transport his victims to the hotel's basement.

The basement featured a dissecting table, stretching rack and industrial oven. Holmes would often dissect his victims and strip them of their flesh. He would then cash in and sell their bones to medical schools as human skeleton models.

In some cases he would cremate his victims or throw them into acid.

Other features of the hotel of horrors included trap doors, peepholes and stairways that led nowhere.

Holmes killed dozens of people at the hotel when the World's Fair came to Chicago in 1893.

During his horrific murdering spree, the wealthy doctor was also travelling across the country committing insurance scams. He abandoned the hotel after the World's Fair to primarily focus on collecting money via scams.

He was arrested and sent to jail after he was caught stealing horses from Texas and selling them in St Louis. After he was released from jail, he murdered his former insurance scam business partner Benjamin Pitezel.

Benjemin Pitezel (and some of his family) met a tragic end.

It was Pitezel's murder that led to Holmes' death sentence in Philadelphia in 1896.

Police eventually came across the hotel of horrors when they were investigating Holmes. Authorities found it difficult to count exactly how many bodies were in the hotel because they were so badly dismembered and decomposed.

The exhumation and DNA analysis will be performed by the Anthropology Department at the University of Pennsylvania. The great-great-grandchildren, John and Richard Mudgett and Cynthia Mudgett Soriano, all of California, submitted DNA samples to the university, according to their petition seeking the exhumation.

Judge Chad Kenney's order states that the remains are to be re-interred in the same grave after testing, whether or not they belong to Holmes.

John Mudgett's wife said by phone from California Wednesday that the descendants weren't commenting. They're related to Holmes through his son with his first wife, Clara Lovering.

Holmes was executed in a public event at Philadelphia's Moyamensing Prison on May 7, 1896. Witnesses said he maintained his cool to the very end, even telling the executioner not to rush. The New York Times reported it took Holmes more than 15 minutes to die.

The body of 19th century serial killer Dr HH Holmes is being exhumed from the cemetery in suburban Philadelpha. Photo/AP

Holmes had left specific instructions for his burial. He was to be laid in a pine box and the box was then filled with cement, buried 10 feet in the ground and covered again with cement.

Despite it all, rumours started swirling that he'd managed to swap another convict to be executed in his place, and he went free.

The hotel of horrors was remodelled as an attraction known as the Holmes Horror Castle but it burned down before it could open.

Holmes had been married to three women and had an unknown number of children.

He was the subject of the 2003 best-selling book, The Devil in the White City, by Erik Larson.