ROME, March 3 (Reuters) - Top mafia boss Matteo Messina Denaro was captured thanks in part to a hand-written note found hidden in his older sister's house, judicial documents show, after police arrested the woman on Friday.
Rosalia (Rosetta) Messina Denaro, 67, was detained in Sicily on mafia membership charges, Carabinieri police said, releasing a 57-page arrest warrant.
Her brother, Matteo Messina Denaro, 60, was Italy's most wanted man until his arrest on Jan. 16, after 30 years on the run. He was caught in Palermo, outside a private clinic for cancer patients.
A month earlier, police had found the note inside the leg of an aluminium chair in Rosalia's home in the western Sicilian town of Castelvetrano, the arrest warrant said.
Officers had stumbled on it during a covert operation to plant listening and video recording devices, one of which was meant to go inside the chair.
Police photographed the note, which initially seemed an unintelligible jumble of words, signs and letters, and replaced it where they found it. Analysis showed it chronicled a man's struggle with colon cancer.
Italian authorities had already said that Messina Denaro was snared by his failing health, but on Friday they revealed the source of the key tip.
The "historic result of the capture ... originated from a note, imprudently kept, albeit hidden, by Rosetta," a judge wrote in the warrant.
Police presumed that the note referred to a relative, and focused on Matteo after verifying that no other family member had similar cancer problems.
Matteo Messina Denaro used a fake identity, but police unmasked him after discovering that the man whose identity he stole was not in hospital when records suggested he should have been there.
The mobster has been convicted for a long list of crimes, including the killings of top prosecutors Giovanni Falcone and Paolo Borsellino and of a teenage boy whose body was dissolved in acid.
'BIG STRAWBERRY'
While on the run, Messina Denaro followed mafia tradition in communicating with relatives and affiliates via "pizzini", small pieces of paper sometimes written in code.
His sister was one of the people who handled the "pizzini", but did not follow her brother's recommendation to burn them after use, police said.
They allege she had a major role in her mafia family, acting as treasurer, and said she communicated with Messina Denaro using the code name "Fragolone", or "big strawberry."
Her home was decorated with a large portrait painting of her fugitive brother, showing him wearing sunglasses and a crown, a police video showed.
Rosalia's husband, Filippo Guttadauro, is another convicted Sicilian mobster, while her daughter Lorenza is Matteo Messina Denaro's defence lawyer.
The warrant described her as a woman with "origins and traditions all inspired by an orthodox and rock-hard mafia culture".
