Could Andrew Mountbatten-Windsor face charges? An expert says the process is difficult

Andrew Mountbatten-Windsor could face life imprisonment if he is charged with misconduct in public office, but a legal expert warns it is a difficult offence to prove.

The disgraced former prince has been released from about 11 hours of custody pending an investigation into suspicion of misconduct in public office after he was arrested at his Sandringham home about 8am today (7pm AEDT yesterday).

Loughborough University's expert in public law Dr Tom Frost said Mountbatten-Windsor was likely interviewed under police caution.

READ MORE: 'This is unprecedented': King's brother in custody as two addresses searched

"The arrest of Andrew Mountbatten-Windsor is an unprecedented event. He is the first senior member of the modern Royal Family to be arrested," he said.

"This is likely the most serious arrest of a member of the Royal Family since that of King Charles I for treason in January 1649."

Frost explained misconduct in public office is a "very serious common law crime" which could face trial by a jury if charges are laid.

The offence holds a maximum sentence of life imprisonment.

"It should be stated that this is still a very early stage of the investigation," he said.

"In English law, every individual is presumed innocent until proven guilty in a court of law. An arrest does not necessarily mean an individual will be charged by the Crown Prosecution Service."

Frost said an arrest does not necessarily mean Mountbatten-Windsor will be charged by the Crown Prosecution Service as the branch faces several processes and difficulties.

READ MORE: What happens next after Andrew Mountbatten-Windsor arrested

The Crown Prosecution Service has to assess whether to press charges under section four of the Code for Crown Prosecutors, also known as the full code test.

According to the code, the full code test should be applied only "when all outstanding reasonable lines of inquiry have been pursued".

The full code test has two stages - the evidential stage and the public interest stage.

The Crown Prosecution Service must determine whether there is enough evidence to provide a realistic prospect of conviction and then whether that course of action is required in the public interest.

They will need to consider several factors, like the seriousness of the offence, the impact and harm to the victim, the impact on the community and whether sources of information require protection.

Frost said misconduct in public office is a difficult offence to prove for senior executives or senior political figures.

"There remains a high threshold before criminal proceedings can be brought for this offence," he said.

READ MORE: How Andrew went from helicopter pilot to trade envoy to royal pariah

Currently, the Public Office (Accountability) Bill is before parliament to replace the old common law offence with new offences to make it easier to hold senior executives and senior political figures to account.

Frost warned that if Mountbatten-Windsor is charged, it will be under the old common law.

Police have searched addresses in Norfolk and Berkshire.

Mountbatten-Windsor's Sandringham home is in Norfolk and his former home at the Royal Lodge is in Berkshire, but police have not confirmed whether those were the locations searched.

His brother, King Charles III, has offered his "full and wholehearted support and co-operation" to the investigation.

"What now follows is the full, fair and proper process by which this issue is investigated in the appropriate manner and by the appropriate authorities," he said in a statement.

"Let me state clearly: the law must take its course."

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