PARIS, Dec 24 (Reuters) - Charles Sobhraj, a convicted killer who police believe killed more than 20 western backpackers on the "hippie trail" through Asia in the 1970s and 1980s, returned to France on Saturday after nearly two decades behind bars in Nepal.Nepal's Supreme Court ordered the release of Sobhraj, known as the "bikini killer" in Thailand, and 'The Serpent" for his evasion of police, on Wednesday citing his advanced age and health.Asked what his next steps would be, she said: "He will file a legal complaint against Nepal because the whole case against him was fabricated."Sobhraj had been held in a high-security prison in Nepal since 2003, when he was arrested on charges of murdering American backpacker Connie Jo Bronzich in 1975.But he was suspected of more murders, including in Thailand, where police say he killed six women in the 1970s, some of whom turned up dead on a beach near the resort of Pattaya."