A man who spent years in solitary confinement for a drink-driving offence without ever being prosecuted has been awarded $15.5m (£10.3m) in compensation.

Stephen Slevin, 59, from New Mexixo, successfully sued Dona Ana county because he had been left in his cell for two years. He lost a third of his body weight, his beard had grown down to his chest, his toenails curled around his feet and fungus grew on his skin because he was deprived of showers.

He was even forced to pull one of his own teeth during his time in solitary confinement as the guards refused to get him to a dentist.

Slevin was originally awarded $22m last year but prison authorities appealed against the original amount, which has now been reduced.

Slevin will receive a one-off payment of $6m, with the rest in instalments. The money awarded to Slevin is one of the largest federal civil rights settlements in history involving an inmate.

Matt Coyte, Slevin's lawyer, said: "His mental health has been severely compromised from the time he was in that facility. That continues to be the same. No amount of money will bring back what they took away from him.

"But it's nice to be able to get him some money so he can improve where he is in life and move on."

Slevin, who has lung cancer, told KOB4-TV: "Why they did what they did I'll never know.

"Walking by me, watching me deteriorate day after day after day, and they did nothing at all to get me help."

Slevin was arrested in 24 2005 on charges of drink driving and receiving a stolen vehicle.

Although physically healthy when he entered the jail, Slevin made frequent requests to see a doctor and for medication to help treat his depression, all of which were ignored until just a few weeks before his release.

The lack of medical attention and solitary confinement pushed Slevin further into depression.

His lawyer described his experience as the "worst case of solitary confinement" ever seen in the US.