Jane Dorotik was convicted of her husband's murder but says some so-called bloodstains presented at trial were never tested and others were not blood at all.
The endorsement of President Biden comes as independent candidate Robert F. Kennedy Jr. is calling on his family's ties to the Latino community and the civil rights leader.
Lieberman represented Connecticut for decades and became the first Jewish candidate on a major party ticket. He died Wednesday in New York City at 82 years old.