Janis Sharp, from Brookmans Park, disclosed that journalists and MPs have also been targeted over their involvement in her high profile campaign to prevent her son Gary McKinnon from being extradited.
In a series of emais, an American known only as Jerry describes Asperger’s sufferer Gary as a “ target”.
He also threatens that “future unpleasantness and the death of annoying MPs and journalists… will have been no accident.”
Janis admitted that receiving the threatening emails had saddened her.
But she vowed: “I refuse to be intimidated and will continue to fight for my son to be tried in the UK.
“If any British person was issuing death threats against American politicians, journalists and members of the public they would probably be charged with terrorism and extradited to America to face a lengthy prison sentence.”
The threats are currently being investigated by the Metropolitan police forces.
Meanwhile, the parliamentary authorities have also been informed after a message was sent to Hertsmere MP James Clappison.
Security at the House of Commons may now be stepped up as a result.
Another prominent MP has also been targeted, along with journalists from three national newspapers.
Det insp Chris Wright, investigating, said: “Hertfordshire Constabulary takes all allegations of crime seriously and this case is no different.
“The origins of these threats are being investigated and we are currently following a number of lines of enquiry into the matter.”
A Metropolitan Police spokeswoman added that detectives were “liaising with US law enforcement agencies” after a number of “malicious emails” were sent to various media agencies.
Prosecutors in America allege Gary, 43, caused nearly £500,000 worth of damage to military computers in 2001 and 2002.
If convicted in a US court, he could face up to 60 years in jail.
Gary, of North London, admits hacking but maintains he was looking for evidence of alien life.