Ravi Rutnah said things were "not adding up" and he would be requesting an independent inquiry at the next court appearance of the three men who have been charged.
The prime minister and president of Mauritius are pushing for the reintroduction of the death penalty after the killing.
The three hotel employees are due in court on Wednesday for a short procedural hearing.
Mr Rutnah -- who is representing Abinash Treebhoowoon -- said he had "doubts over a lot of things".
Mr Treebhoowoon has made a confession to police about his part in the crime, but Mr Rutnah has raised serious concerns about how this was obtained.
It is being alleged Mr Treebhoowoon went into the room with a work colleague with the intention of stealing money and killed Michaela when they were disturbed.
"We are going to make a complaint against the police on Wednesday and also a complaint about the investigation here," said Mr Rutnah.
At the men's first court appearance, Mr Rutnah sought and was granted an inquiry into allegations of police brutality against his client.
"I was not allowed to advise my client on his constitutional rights," he said. "I doubt very much everything that was said (in the confession)."
He said he was present when the 29-year-old signed the confession -- but he said the police read out the statement based on previous interviews and he never heard his client verbalise his confession. "I could see the physical pressure on him and also on me," he said.
A second barrister for the room attendant was reportedly threatened with jail when he tried to advise his client that it was his right to remain silent.
"Everything was basically moulded, prepared for him," added Mr Rutnah.
He said he was also bringing the matter to the attention of the International Human Rights Commission, the International Bar Association and the Bar Council in Mauritius.
Investigating officers have denied any allegations of police brutality or impropriety.
Ranjit Jokoo, investigating officer with the Major Criminal Investigation Team, said they were continuing to interrogate one of the accused, Sandip Moneea, who has not yet made a confession.
Raj Theekoy, who has been charged with conspiracy to murder, has made a confession to police. The families of all three men have protested their innocence.
Yesterday, the brutal killing remained front-page news.
Newspapers reported how the president and prime minister wanted the death penalty reintroduced. It was abolished in 1995.
Prime Minister Navin Ramgoolam also gave a guarantee that whoever killed Michaela "would be caught".