An undercover Panorama investigation has found some paid expert witnesses prepared to provide helpful court reports despite a client's confession.

Only one of nine expert witnesses approached did not want to get involved after the reporters admitted "guilt".

They included animal expert Prof Barry Peachey who suggested a false defence for a reporter who "confessed" to interfering with a badger sett.

He later insisted his report was truthful and accurate.

Expert witnesses produce reports for use in court whenever specialist knowledge is required.

They are bound by ethical duties and legal rules, which state their reports should be independent and impartial, even though they are often paid for by only one side or the other.

Their reports should include all relevant information provided by the client.

Secret filming

Four of the expert witnesses Panorama approached provided court-ready reports. All were caught on camera flouting the rules.

One was animal scientist Prof Barry Peachey, who specialises in the law protecting badgers.

Panorama: Find out more Image copyright bbc Daniel Foggo presents Undercover: Justice for Sale?

BBC One, Monday 9 June at 19.30 BST Then available in the UK on the BBC iPlayer

The reporter told him he had deliberately put a dog in a sett in pursuit of a badger, an offence that can carry a six-month jail sentence. He said he feared he had been filmed by a passer-by and could face prosecution.

During the secret filming, Prof Peachey acknowledged the reporter had broken the law.

"What you've done and what they can prove are two entirely different things," he told him.

He continued: "Your defence is that this was a pure accident… You were walking your dog along and the dog suddenly saw a badger and dived down a hole and all you were trying to do is get it back."

He then produced a report for use in court, which correctly described the badger sett as active, but which also set up the false defence by saying the sett was not visible to the casual passer-by.

Prof Peachey also said he would be willing to give evidence in court saying that it was "highly likely" the dog entered the sett by accident.

In total he charged £2,223 for his report.

He said his report was truthful and accurate and he had no financial incentive not to tell the truth. He said the facts of the incident had not been made clear and he would never lie in court.

'Surprising'

Undercover reporters also approached two handwriting experts, confessing that they had written an anonymous, threatening note but wanted reports to cast doubt on their guilt.

The breaches of duty are, had they been carried through into the court process, very serious Timothy Dutton QC, Former chairman of the Bar Council

Simone Tennant, a graphologist, ignored some evidence that would have been unhelpful to the reporter and concluded that the authorship of the note was "inconclusive".

She did not respond to Panorama's findings.

The other expert, Michael Ansell, a former deputy head of the Metropolitan Police's document section, said that there was "strong evidence" the reporter had not written the note.

He later said although he heard the reporter say he had written the note, he did not think he meant it.

Neither expert mentioned the reporters' confessions in their reports.

Timothy Dutton QC, former chair of the Bar Council and an expert in legal ethics said it was comparatively rare to encounter experts who sought to subvert the rules.

He added: "Nevertheless, seeing these examples is surprising and in each of these instances it seems to me that the breaches of duty are, had they been carried through into the court process, very serious."

As an industry, expert witnesses are subject to very limited regulation and there are calls for greater powers to police them.

Last year, the Ministry of Justice rejected a proposal from the Law Commission to bring in a new law giving courts greater powers of scrutiny of expert testimony.

However, Justice Minister Damian Green said: "Rules for criminal courts are being tightened and changed so judges are provided with more information at an early stage about any expert evidence being used, giving them the opportunity to challenge anything inappropriate."

Watch Panorama, Undercover: Justice for Sale? on BBC One on 9 June at 19:30 BST.