A breakdancer and a “body mechanics expert” were hired for £8,400 during a probe into a musician’s death in police custody.
Schizophrenic Sean Rigg, 40, died of a cardiac arrest after being restrained at Brixton police station in 2008.
A 2012 inquest jury ruled police used “unsuitable force” and the case sparked a campaign for better treatment of mentally ill suspects.
The breakdancer and body mechanics expert were recruited to assess police claims Mr Rigg had hurt himself while “spinning” in a force van.
They suggested this caused his injuries, rather than excessive force during the arrest.

Last night bobbies’ union the Police Federation criticised the decision – and blasted the 11-year probe for putting cops “through hell” for so long.
They spoke out after a Met panel finally cleared five officers of misconduct in March.
Spokesman Phil Matthews said: “The case is a fine example of them assuming the police officer was guilty from the outset. They threw good money after bad trying to prove their assumptions and theories.”
The federation wants a one-year time limit to speed up investigations.
Mr Matthews added: “The officers in the Rigg case are all broken individuals.”
The case was investigated by the Independent Police Complaints Commission, which was replaced last year by the Independent Office for Police Conduct.
Its conclusions clashed with the inquest so top criminologist Dr Silvia Casale was hired to carry out a review in 2013.
A spokesman said: “Dr Casale commissioned a body movement expert to determine whether the police witness accounts that Mr Rigg was spinning in the back of the police van were plausible.
“Following the Casale review, the IPCC investigation was reopened. As part of this the IPCC incorporated evidence that had emerged from both the inquest and the review.
“The police officers were re-interviewed and asked again about the evidence regarding Mr Rigg’s actions in the police van. As part of this process the evidence collected by the Casale review was put to them as is entirely proper as part of the evidence disclosure process.”
He added: “We have acknowledged the need to improve the timeliness of investigations.”