Movies often celebrate perseverance. We love underdogs, and unlikely heroes who pull themselves up by their bootstraps, enduring any number of roadblocks on the way to achieving a goal. Tony Goldwyn’s Conviction -- the main character’s unflagging determination is built right into the title -- is all about this trait. As children, Betty Anne Waters (Hilary Swank) and her brother, Kenny (Sam Rockwell), survived bad parenting and poverty by leaning on each other for support. Kenny grows up to be something of a troublemaker, eventually being convicted for a murder he swears he didn’t commit. His sister believes him and, without even a high-school diploma, sets about going to law school in order to figure out a way to free him. She gets a GED, then graduates law school with the help of her only friend (Minnie Driver). She eventually gets the attention of O.J. Simpson defense attorney Barry Scheck (Peter Gallagher), who runs an organization devoted to overturning wrongful convictions by analyzing DNA evidence with tests that were unavailable at the time the cases were tried. When he agrees to help her -- if she can find the old blood evidence -- Betty plows her way through the legal complications that stand between her brother and his freedom. On the page, Pamela Gray’s script hits every familiar note to make Betty’s life as difficult as possible. The problem is that while Betty’s life is flawed, she herself is flawless. If we are supposed to emulate her courage, there need to be some scenes showing she’s a flawed human being. As played by Swank, Betty is a classic teary but strong-willed heroine, not unlike those at the center of a Lifetime movie -- her seemingly inexhaustible capacity for selflessness defines her. The character’s situation is interesting, but the character isn’t because we can’t relate to her. Luckily, Sam Rockwell gives the movie some drive as her ne’er-do-well brother. He’s a hard-drinking rabble-rouser, prone to bar fights and getting naked in public for a laugh. Rockwell lets us see the effects of Kenny’s dysfunctional childhood in the character’s impulsivity and occasional fatalism. We’re fairly sure we can believe Kenny most of the time, but we’re never really 100 percent sure like Betty is, and that friction gives the movie some life. The filmmakers were smart to let a good chunk of the film’s emotional payoff come from scenes where Kenny makes peace with the teenage daughter who was just an infant when he went to jail, because their relationship is more complex and compelling than the always-perfect bond between Kenny and Betty. If there were more of Rockwell, Conviction might be able to escape the straightforward obviousness that keeps it from being little more than a well-made but not very interesting TV movie.