Five West Papuan men are facing 15 years or more in jail for raising the banned morning star flag, while a sixth man has been deemed unfit to face trial after being beaten by security forces so badly that he now has mental health issues, according to the group’s lawyer.

In Biak, a small island off the northern coast of West Papua, the public prosecutor has recommended Oktovianus Warnares, 41, receive 18 years in prison while his co-accused George Simyapen, 49, Yoseph Arwakon, 40, Jantje Wamaer 40, and Markus Sawias, 20, are each facing 15 years.

The trial of a sixth man, Yohanes Boseren, 20, has been suspended because the defendant is suffering from mental health problems after being beaten by Indonesian security forces, according to West Papuan human rights lawyer Gustaf Kawer, who is representing the group.

The men were arrested after the Indonesian police and military opened fire into a crowd of people gathered for a flag-raising ceremony on 1 May 2013, the 50th anniversary of Indonesia’s annexation of West Papua, Kawer said.

“The defendants were holding a protest and security forces responded violently by shooting, beating and torturing them,” he said.

“The sentence demanded by the prosecutor is totally over the top.”

The chief of police in Biak did not respond to numerous requests for comment.

Esther Cann, campaign co-ordinator for the UK-based advocacy group Tapol, which has been closely following the case, called the proposed sentences against the five men “draconian”. She said the situation facing Boseren was particularly shocking.

“Yohanes was beaten up so badly on arrest, including blows to the head, that he developed a sort of mental illness, and just isn’t really present,” Cann said.

“The court eventually begrudgingly concluded that his trial be suspended, but he’s not being given anything like adequate treatment. He’s taken to hospital for a couple of days, probably sedated, and then is now back in prison again.

“We’re very concerned about that and we think he should be released immediately – as should the other detainees,” she said.

The defence in the trial of the five men will begin its case in Biak court today.

Meanwhile, the high-profile West Papuan political prisoner Filep Karma, who has served nine years of a 15-year sentence, also for raising the morning star flag, has called on Australians to lobby the Abbott government to change its policies on West Papua.

In a video interview with Izzy Brown, from the West Papua Freedom Flotilla, Karma said Australia’s decision in September last year to deport a group of West Papuan asylum seekers to Papua New Guinea without hearing their legitimate claims for asylum had been “hurtful”.

“Australia is the closest neighbour, so why did its government do this to us?”

“I hope that every Australian shows their support for West Papua, by pressuring the Australian government to amend its policies towards West Papuans,” he said.