DNA evidence frequently exonerates wrongly convicted people. It also frequently reveals that someone who was convicted of one offense was also guilty of committing many other offenses for which the offender was never convicted.
For example, genetic tests on evidence from a 1969 rape and murder case that was solved last month revealed that the offender who died in 2001, seventeen years ago, also committed many other serious crimes.
Sumpter lived in Cambridge as a young child, dated a girl in Cambridge in the mid-1960s and, in 1967, was working on Arrow Street – just a mile from [the 1969 victim] Jane Britton’s apartment.Sumpter was arrested and convicted of physically assaulting a woman he met at the Harvard Square MBTA station three years after Jane’s murder.But in 1975, Sumpter was out of jail and raped a woman in her Boston apartment. It was then that he was sent to prison for 15-20 years.Just 13 months after he was paroled, Sumpter died on Cancer in 2001.After his death, Sumpter’s DNA profile was matched to the rape and murder of 23-year-old Ellen Rutchick in her Beacon Street Apartment in 1972. He was also connected to the 1973 rape and murder of 24-year-old Mary Lee McClain in her Mount Vernon Street Apartment.He was also eventually connected to a 1985 rape, which police say he committed after escaping from work release.
So, after the 1969 rape and murder, he committed at least two more rape and murder offenses, a physical assault of a woman, an at least two more rapes that did not result in the death of the victim, a total of at least six violent felonies and one escape, five in a five year period, and two more in related incidents in a single year.
Yet, he was is prison for the lion's share of the time he wasn't on the streets committing crimes. He was probably only free of correctional supervision (either escaped or in custody) for seven out of his short thirty-two years of adult life and probably never went more than two years as an adult while he was not incarcerated without committing a felony.
It is also likely that the felonies that DNA evidence has linked him to weren't the only ones that he committed. Evidence collection standards in the 1970s were as good as they are now, not all crimes leave traces of DNA evidence, and not all cold cases where DNA tests could be done are tested before the evidence is destroyed or too degraded to test. It is quite likely that he actually committed at least two or three more felonies.
Catching serious felon and incarcerating him (or her) for a sustained period of time probably does prevent a great many future crimes. But, this approach can also work grave injustices if the person convicted and sentenced for a long period of time wasn't actually guilty of the crime in question.
If DNA technology has been available and successful in convicting him of his first known felony in 1969 (although realistically no one starts their criminal career with the violent rape and murder of a stranger in her apartment as a first crime), many people in the future could have been spared.