Convicted of murder, jailed for three years and then finally acquitted, Gordon Wood is suing the state of New South Wales for malicious prosecution and wrongful imprisonment.

Mr Wood spent more than three years behind bars after being convicted of killing Caroline Byrne, his then girlfriend, by throwing her off a cliff at notorious Sydney suicide spot The Gap in June 1995. His conviction was overturned in 2012.

So, what does he have to prove for his current case to succeed?

"Malicious prosecution is a civil suit that you can bring and there are broadly four elements to it," Professor David Rolph from the Sydney Law School at the University of Sydney said.

"The person [or body] that you are suing has to have prosecuted you, usually for a criminal offence, and that prosecution has to have been terminated in your favour.

"Then you have to prove that the person who prosecuted you acted with malice, which is improper motive, and that the prosecution against you was brought or maintained without reasonable and probable cause."

Professor Rolph said establishing all of those elements can be difficult.

"Because the onus of proof rests with the person suing, there's a high degree of difficulty, particularly in relation to that element of malice," he said.

"If the prosecution can demonstrate that they were simply invoking the ordinary processes of the criminal law, then that is usually sufficient to prevent a plaintiff from proving malice."

Difficult to prove, but not impossible: expert

In 2015, Roseanne Beckett won her case for malicious prosecution, after being wrongfully convicted of plotting to kill her husband in 1991 and spending 10 years in jail.

The state of NSW was ordered to pay her just over $4 million in damages, including interest and her legal costs.

Journalist Wendy Bacon followed Ms Beckett's long legal battle.

"It is extremely difficult to win these cases and most people don't have the resources," she said.

"It is hard to mount a case from prison unless you can get the media interested, as in Roseanne Beckett's case."

Roseanne Beckett, centre, leaves the NSW Supreme Court with supporters in 2015. ( AAP: Dean Lewins )

According to Professor Rolph, malicious prosecution cases were more common than you might think.

"It's a very well-established tort, it goes back a number of centuries," he said.

"The common law has for a very long period of time protected the liberty of the individual and this is an important aspect of protecting those rights."

He said that, as in the case of Gordon Wood, actions for malicious prosecution often go hand in hand with actions for false imprisonment.

"So you say that because you maliciously prosecuted me, I was then also falsely imprisoned," Professor Rolph said.

"You didn't have a reason to imprison me, so you maliciously prosecuted me and deprived me of my liberty and so therefore I should be awarded damages."