A court hears testimony from the victim’s sister, who told police she became concerned about her sister’s welfare as the relationship with her boyfriend deteriorated. The sister, Arleta Derkacz, says she told authorities that the marine engineer boyfriend had previously strangled the victim. She linked her growing worry to the alleged history of violence within the relationship. Prosecutors’ case, as described in reporting, centers on events leading up to the victim’s death, with the allegation that she was raped and murdered. The sister’s evidence is presented as part of the broader account of the relationship and the reasons she believed the victim was at risk. The reporting provided does not include further details of the boyfriend’s response or any corroborating evidence in the excerpts, focusing instead on what the sister told police about prior strangling and the worsening relationship. The matter is being heard in court, with the testimony forming part of the evidence considered by the court.