The suspect in the death of Harry Dunn is to be sued by his family in the US using a 245-year-old English law.

Harry's parents, Tim and Charlotte, arrive in the US this week to meet with their lawyer and finalise arrangements for the civil suit against Anne Sacoolas, which will be submitted in a court in Virginia, where the American currently lives.

She went to the US claiming diplomatic immunity while under investigation after a car she was driving struck a motorcycle ridden by Harry, 19, outside RAF Croughton in Northamptonshire in August.

Agnieska Fryszman, the Dunns' lawyer in the US, told MailOnline: 'It's quite ironic that our civil suit is relying on ancient English common law on transitory tort.

'This establishes the right of individuals to take action anywhere regardless of where an incident might have taken place.

'This law was established in England and later upheld in the US. Ms Sacoolas left England for Virginia, which means we are entitled to sue her there.'

The legal precedent the Dunns' lawyer is relying upon dates back to a case from 1774 in which Anthony Fabrigas sued John Mostyn for offences committed in Minorca.

Charlotte Charles and Tim Dunn, Harry's parents, will try to sue the US suspect of their son's death using a 245-year-old English law

Harry Dunn, 19, was riding a motorcycle outside RAF Croughton in Northamptonshire in August when he was struck and killed by Anne Sacoolas

Agnieska Fryszman (left), the Dunns' lawyer in the US, told MailOnline she will try to use legal precedent relying upon dates back to a case from 1774 in her case against Ms Sacoolas (right)

The legal precedent the lawyer is relying upon dates back to a case from 1774 in which Anthony Fabrigas sued John Mostyn for offences committed in Minorca.

Mr Mostyn was governor of the island at a time but an appeal court in London upheld a decision that he should pay £3,000 in damages even though the offences had not been committed in England.

In a subsequent US case from 1843, the country's Supreme Court relied on the British case and established the right of actions against an individual to be brought in one country even though the offence may have been committed in another.

Ms Fryszman, who works for the Washington DC law firm Cohen Milstein, also revealed that the civil suit would include Ms Sacoolas's husband Jonathan, a US intelligence official who was based at the RAF base.

Five members of Harry's family will be bringing the civil suit; his parents, their partners and twin brother Niall.

Ms Fryszman added: 'It may end up actually being more but at this stage, only these five are involved. We will be suing for emotional distress and wrongful death.

The Dunns have also launched legal action in the UK against the Foreign Office, challenging its decision to grant diplomatic immunity to Ms Sacoolas (from left to right: Tim Dunn (Harry's father), Charlotte Charles (Harry's mother), Tracey Dunn and Bruce Charles, arrive at Portcullis House for a meeting with shadow foreign secretary Emily Thornberry)

Five members of Harry's family will be bringing the civil suit; his parents, their partners and twin brother Niall

'There's a limit to what a civil suit can achieve. It cannot make Ms Sacoolas go back to Britain, but it can shine a light on what actually happened and contribute to the justice the family they feel they deserve.'

Ms Frysman refused to be drawn on how much the Dunns plan to sue for, stating that this will be established once she has met with them and finalised the details of the civil case.

Radd Seiger, the Dunn family spokesman added: 'The family expect to be compensated to the full extent of the permissible law.

'Awards of this nature usually run into several million dollars but obviously at this stage, we are not in a position to put a final figure on how much this will be.'

The Dunns have also launched legal action in the UK against the Foreign Office, challenging its decision to grant diplomatic immunity to Ms Sacoolas, which they insist was 'wrong in law.'