Connecticut Governor Dannel Malloy has signed legislation that formally abolishes the death penalty in the northeastern U.S. state.

Malloy signed the bill Wednesday in the state capital of Hartford during a private ceremony attended by anti-death penalty activists, clergy and family members of murder victims. The governor issued a statement saying the moment was a time for “sober reflection, not celebration.”

The bill, passed earlier this month by the Connecticut legislature, replaces the death penalty with a sentence of life in prison without possibility of parole.

Malloy said he came to oppose the death penalty during his years as a prosecuting attorney, seeing “firsthand that our system of justice is very imperfect.” The governor says doing away with capital punishment will ensure it will not be “unfairly imposed.”

The legislation does not exempt 11 prisoners currently awaiting execution, but Malloy said they are “far more likely to die of old age.”

Connecticut is now the 17th U.S. state, as well as the District of Columbia, that does not allow the death penalty, and one of five to abolish it over the last five years, joining Illinois, New York, New Jersey and New Mexico. Voters in California will vote on a referendum to repeal the practice in the November general election.