Speaking for the first time yesterday, Mr Tatschl revealed that he was grilled for two days about Brueckner last year by police investigating Madeleine's disappearance.
The father-of-one, who has returned to his homeland, was interviewed for 14 hours by four detectives at a police station in Graz, southern Austria.
Mr Tatschl, 46, said: 'The detectives were very clear with me from the first minute.
'They said, 'We are investigating Maddie McCann and Christian Brueckner', and I told them I knew why they were here. I was convinced it was him. I know he did it. I was living with him at the time.
'He was my best friend and he was definitely a pervert and more than capable of snatching a child, for sexual kicks or money.'
He thought Brueckner would be arrested shortly after his police interview and said he 'cannot believe' Portuguese detectives have not yet searched the farmhouse they once shared.
'When I saw the Netflix documentary I knew immediately that he was guilty,' he said.
'It was when the female tourist talked about the man turning up at her door where her child was playing, that I knew it was Christian for sure.
'She described him as a creepy guy with acne and blond hair, which fits his description.'
Mr Tatschl said he decided against calling the authorities after watching the documentary because of his dislike of the police and his criminal past.
https://www.dailymail.co.uk/news/article-8445183/I-know-did-Christian-Brueckners-friend-says-German-guilty-taking-Madeleine-McCann.html