Another case I find interesting, although it is technically solved is the Linda Agostini (The Pyjama Girl Case) 1934 - Australia. She was shot and then set on fire. They couldn't identify her so they put her into a formalin tank for 10 years.
After 10 years they pulled her out and had the public look at her again. Linda Agostini's husband was arrested and eventually confessed to the murder of his wife, but insisted that the pajama girl was not his wife, he refused to claim it and after spending 10 years in jail and deported, still insisted the body wasn't his wife's.
Meanwhile during this entire time another woman had been claiming the body was that of her daughter Philomena Morgan, who she believed was murdered by the son of a high ranking detective.
Very weird. I don't know why he wouldn't admit the body was his wife's if it was. He already served his sentence and was being deported. Why did the police totally ignore a woman who identified the body at the beginning, especially when Philomena's description fit the corpse more so than Linda Agostini did.