In a scathing attack on an alleged "dirty game" played by the island's Legends Hotel, a police chief claimed the honeymooner's husband was initially arrested as a suspect because information that would have eliminated him from inquiries was withheld from detectives.
Assistant Commissioner of Police Yoosoof Soopun further alleged that management provided material to "the defence" which it should have given to police.
He was giving evidence on Tuesday at the trial of the two former Legends employees accused of the crime.
Former Legends room attendant Avinash Treebhoowoon, 31, and floor supervisor Sandip Moneea, 42, deny murdering the daughter of Tyrone Gaelic football boss Mickey Harte inside her deluxe room in January 2011.
The prosecution claim they attacked her when she walked in and caught them stealing.
Mr Soopun, who led the murder investigation, repeatedly criticised the hotel while on the witness stand in the Supreme Court in Port Louis.
At one point he told judge Mr Justice Prithviraj Fecknah: "Here I want to state my Lord that the hotel management, as I said from the very beginning there was much concern to protect the reputation of the hotel rather than to discover who has killed the deceased.
"This is why my Lord several important things have never been disclosed to the police."
Testifying as a prosecution witness, Mr Soopun claimed one of the first instances of the hotel's uncooperative stance was when officers were not given records of entries to room 1025 where the newlywed's body was found.
I just want to state that hotel management, particularly the chief security officer Mr (Mohammad) Imrit, has played a dirty game with the police.
Assistant Commissioner of Police Yoosoof Soopun
Mr Soopun said if that data had been available to officers at the outset then the victim's husband John McAreavey would never have been detained.
The widower was handcuffed and left alone in a police station for hours in the wake of his wife's death.
Mr Soopun said the reading from the electronic door entry system was handed over only after "persistent requests".
Mr Soopun said he was "astonished" to find Mr McAreavey later that night handcuffed in the police station.
"He was crying and completely broken," he added.
He said that he immediately gave an order for him to be released.
The officer explained that later that night a sentry was placed outside the room Mr McAreavey had been taken to at Legends for his own safety.
Mr Soopun, who is in charge of the police's major crime investigation team (MCIT), rejected a claim by one of the accused, Avinash Treebhoowoon, that he threatened him with a revolver and told him he would die if he did not confess.
It also emerged that another hotel employee, Seenarain Mungroo, who was originally arrested over the crime and then released is now suing the police and Mauritian state over his treatment.
Mr Soopun was also asked by state prosecutor Mehdi Manrakhan to comment on a claim by Mr Imrit that police had failed to interview a German couple staying at the hotel who indicated they had something to tell officers.
"This is totally unfounded, it's totally not true," he said.
He added: "No Mr Imrit is lying, this shows the bad faith of Mr Imrit."
When questioned by Rama Valayden, representing Moneea, if tests were conducted to see if the room key cards found in the room were actually for 1025, Mr Soopun stated: "We didn't have the co-operation of the hotel management, it's unfortunate to have to tell this in court here.
"Hotel management has not co-operated with police yet they have communicated all the information to the defence."
The trial continues.