The family of a mentally-ill church caretaker who died after collapsing in custody have welcomed the decision to charge a sergeant and two civilian staff with manslaughter, saying they were "cautiously optimistic that justice will be done".

Schizophrenic Thomas Orchard, 32, died more than two years ago after being arrested in Exeter by officers from Devon and Cornwall Police on suspicion of a public order offence.

He was allegedly the victim of "unreasonable force" and when he was found unresponsive in his cell at a police station in the city, he was taken to hospital where he died a week later from head injuries.

The Independent Police Complaints Commission (IPCC) launched an inquiry and after sending a file of evidence to the Crown Prosecution Service last year, prosecutors have announced that three members of staff have been charged.

Sergeant Jan Kingshott and custody detention officers Simon Tansley and Michael Marsden are accused of Mr Orchard's manslaughter, as well as misconduct in public office.

The trio, who have been suspended from duty, will appear before Exeter Magistrates' Court on January 29.

The three officers face two different manslaughter charges.

The first alleges that between October 2 and 11 2012 they unlawfully killed Mr Orchard by the use of unreasonable force.

The second charge states that between October 2 and 11 2012 they unlawfully killed Mr Orchard by gross negligence.

The final charge, of misconduct in a public office, states that the three officers wilfully misconducted themselves in relation to their dealings with Mr Orchard on October 3.

Malcolm McHaffie, deputy head of special crime at the Crown Prosecution Service, said there was insufficient evidence to bring charges against three constables and a custody nurse employed by Serco.

"The decision to prosecute was reached after careful consideration of the evidence and was taken in accordance with the code for Crown prosecutors," he said.

"We have determined that there is sufficient evidence to give rise to a realistic prospect of conviction and that a prosecution is in the public interest."

Mr Orchard's family said in a statement released by campaign group Inquest: "We welcome today's decision and it makes us cautiously optimistic that justice will be done for our much-loved son and brother.

"Most importantly, we think that members of the public will get the chance to decide questions of criminal responsibility.

"Public trust in the police force and the justice system demands a robust prosecution and we hope that the public will be interested in this case and join us in our demand for rigour and fairness from our justice system.

"Our thoughts today are also with the families of others who have died in police custody and who feel that there should have also been prosecutions in their cases.

"Whilst we know they will be happy for us, we understand that today's news will have increased their sense of injustice and their feelings of frustration.

"We can only hope that this decision to prosecute heralds a more robust approach by the IPCC and CPS to deaths in police custody in the future."

Solicitor Beth Handley, who represents the family, said: "Justice requires that the criminal justice process ahead should proceed both robustly and speedily.

"A decision is still awaited as to whether the chief constable should face corporate manslaughter and/or health and safety charges on behalf of Devon and Cornwall Police."

Chief Constable Shaun Sawyer said his thoughts were with Mr Orchard's family "at this difficult time".

"The two-year-long investigation that has followed has been difficult for all of those involved," he said.

"The force and all officers and staff involved have fully co-operated with investigators from the IPCC and, latterly, the Health and Safety Executive throughout their investigation.

"We also await further information from the CPS regarding any potential corporate proceedings against the force.

"In due course, a report will be produced by the IPCC which will provide us with an opportunity to understand if there are any lessons to be learned which have not already been addressed by the force."