A man is suing a cryonics 'life extension foundation' for failing to freeze his father's body – preserving only the head – and sending the rest of his decapitated, cremated remains home in an unexpected package.

Laurence Pilgeram passed away at his home in California in April 2015 after a cardiac arrest. He was 90 years old, and wore a bracelet indicating his body was to be cryonically preserved at the time of his death.

Unfortunately, things didn't go according to plan.

Pilgeram – a prominent biochemist and physiology researcher with a keen interest in the science of ageing – died late on a Friday, and the company he had engaged to preserve him for future revival couldn't be reached until after the weekend.

The cryonics lab contracted to freeze Pilgeram's body – Alcor Life Extension Foundation, based in Phoenix, Arizona – only found out about his passing the following Monday, after his corpse spent the weekend at the medical examiner's office in Santa Barbara.

"Fortunately, no autopsy was performed which at least eliminated any invasive damage but the lengthy delay led to a straight freeze as the only remaining option," a post on Alcor's web site states.

"He was immediately covered with dry ice, per our request," the post continues, going on to explain that Alcor staff later performed a "neuro separation in the mortuary's prep room".

That's where things get complicated.

According to Pilgeram's son, Kurt Pilgeram, this "neuro separation" – a cryopreservation term for where the head is removed from the rest of the body for freezing (which is cheaper than preserving the whole body) – was never supposed to happen.

According to legal documents obtained by The Telegraph and other news outlets, Kurt Pilgeram was "shocked, horrified and extremely distressed" after receiving an unexpected package from Alcor "which purportedly contained his father's cremated remains, except allegedly for his father's head".

As a result, Kurt Pilgeram is suing Alcor for US$1 million for failing to preserve his father's entire body "no matter how damaged".

"Shockingly, in a addition to cremating [his] remains without any authority, Alcor did not even have the courtesy to notify [Kurt] that his father's remains had been cremated or that they were being shipped to his house," the filing reads.

Legal representatives for Alcor have refused to answer media questions as to why the cryonics firm preserved only Pilgeram's head after his death and not his whole body per the alleged agreement, but court documents supplied by Alcor state the body was "medically unable to be preserved" – presumably due to the length of time that passed before Alcor took possession of the remains.

According to the legal filings, Pilgeram's wishes were that Alcor would "place into suspension any biological remains whatsoever that they may be able to recover, regardless of the severity of the damage to my human remains from such causes as fire, decomposition, autopsy, embalming, or other causes."

In a statement to The Daily Beast, the company's lawyers said: "Alcor cannot specifically comment about this case but Alcor generally is confident that the legal system will properly run its course, as it has in the past."

A trial date is expected to be set in January.