amazing technique called dna or genetic profiling. >> it was a case of eureka. you could solve paternity disputes. >> david baker said, look, let's cement the case against this young man. let's go to this geneticist at lester university, dr. alec jeffries and take the semen samples from both murders and cement the case with his new thing called genetic firing making and prove that he did both of them because we knew he did both of them. >> dr. jeffries didn't know where he could do it or not. this sort of analysis had never been done before. the breakthrough technique is called restriction technique polymorphism. rflp. it can identify an individual just on a small amount of dna,