Police are investigating the murder of Karen Carter, a British-South African woman who was stabbed to death in Trémolat, France.Authorities have seized knives during a raid related to a male suspect described as psychologically disturbed, but no evidence links him to the crime.DNA samples found in Carter's car remain unidentified as the investigation continues, with police exploring various lines of inquiry including the relationships of those closely involved with Carter and her partner, Jean-François Guerrier.