Often leaving unsolved crimes that last for years or even decades, cold case investigations constitute one of the most difficult facets of the criminal justice system. DNA evidence has shown to be a game-changing weapon in resolving such cases in recent years. The passage of time often compromised traditional techniques like eyewitness testimony or physical evidence, but DNA has become a strong, unquestionable connection between offenders and crime scenes. Emphasising developments in forensic technology, including mitochondrial DNA, touch DNA and forensic genealogy, this article investigates the revolutionary influence of DNA analysis in cold case investigations. These developments have enabled the extraction of viable DNA from degraded materials, therefore resolving formerly believed unsolvable cases. The article shows how DNA evidence has given victims' families closure and rebuilt public confidence in the justice system by means of case studies including the Golden State Killer and the Cleveland Strangler. Although the use of DNA evidence has greatly improved, problems still exist including contamination, deterioration, and the possibility of false convictions. This paper also looks at the legal, ethical, and technological issues surrounding DNA use in criminal investigations. In the end, the research shows how important DNA is for contemporary forensic science and how it can provide justice even after many years