The life of legendary radical leftist attorney William Kunstler proves a fascinating topic for new documentary, “William Kunstler: Disturbing the Universe.”

The film debuted at last year’s Sundance Film Festival, then locally at our St. Louis International Film Festival. It is now scheduled to open Friday, Jan. 22 at the Tivoli Theater.

The filmmakers are his own daughters from his second marriage, Emily and Sarah Kunstler. Although there is personal affection, this documentary is no introspective family memoir or one-sided defense. Instead, it is a surprisingly well-balanced and fair exploration of a public figure that people either loved or hated.

Kunstler was a puzzling man who went from the idealism of defending Civil Rights activists to the opposite extreme of defending murderers, organized crime figures and even terrorists, confusing and outraging former supporters, but he was an important figure in a significant historic era.

As the filmmaker daughters make clear immediately, his family was as puzzled, frightened and dismayed as anyone by their father’s changes. As young girls, Emily and Sarah were proud of their father’s history as an attorney who defended Freedom Riders in the Civil Rights era and gained fame for defending the Chicago Seven anti-war protesters at the 1968 Democratic Convention.

But later, the girls were frightened by his newer clients — men accused of rape, murder or cop-killing, and even organized crime figures and terrorists. They became ashamed of what he was doing and, along with their attorney mother, totally mystified about why he was doing it. When their father turned to defending such clients, they were as dismayed and puzzled as his former supporters.

This is the twisted knot that the filmmakers set out to untangle: why would someone so committed to doing good then take to defending such bad people?

Their exploration of Kunstler’s often high-profile life, and this later strange turn, takes us back through his personal life but also on a review of some protest events in this turbulent era, including 1960s Civil Rights lunch counter desegregation activists in the South, anti-Vietnam War protests, the Attica prison riot and American Indian Movement’s stand at Wounded Knee.

The documentary uses home movies and photos, along with archival footage of historic events, to explore Kunstler’s life and times. The well-constructed film has more balance in perspective than you might expect, presenting the unpleasant along with the admirable. There are interviews with a variety of people, eye witnesses and well-known figures of the time, as well as family and colleagues.

The film is so well-crafted and balanced as a documentary, one occasionally forgets that his daughters are telling the story, at least until they return to a more personal touchstone. It is a pleasing mix of personal and historic perspective and gives one clear sense of the times and the person.

In their attempt to understand his later life, Emily and Sarah Kunstler go back to their father’s earlier, pre-activist life. Kunstler, with his first wife and family, lived an ordinary suburban life in New York, practicing law with his brother. He was an “armchair liberal” until he almost inadvertently becomes involved with anti-segregation efforts in the South. But it is his courtroom work defending the Chicago Seven in 1968 that bring him fame and radicalizes him. That event both ends his marriage and launches Kunstler as a kind of rock star rabble-rouser of the left, a role whose public attention he clearly loved.

The documentary explores Kunstler’s particular connection with Michelangelo’s statue of David, which the lawyer described as the only one showing David contemplating his actions before he slew Goliath. Kunstler would tell his daughters he thought David was reflecting that he was about to do something that could endanger his own life but had the potential to do great good, something he felt should have meaning for anyone.

In the ’70s, a second marriage and new family caused Kunstler to seek work closer to home, as a criminal defense attorney in New York. But his new work took an unexpected direction, with Kunstler taking on high-profile but unsavory clients, and seeming to relish taking any contrarian stance. When his daughters would ask why he defended such awful people, he replied that everyone deserved a lawyer, but not why they deserved the famous William Kunstler.

A final straw was reached for many long-time Kunstler supporters with his decision to defend the Palestinian who killed the right-wing Rabbi Meir Kahane. Members of Jewish organizations protested outside his home, causing his embarrassed, frightened family to hide. But Kunstler responded to accusations being called a self-hating Jew with a quip that the one thing everyone knew about him was how much he loved himself.

There is value in trying to understand even unpleasant history and a contradictory figure like Kunstler, especially through such a thoughtful, insightful documentary. Although the film does not give us definitive answers to why he did what he did, we do get a better grasp on both this flawed, contradictory human being and his turbulent, significant times.