Story highlights Clinton says women and their families are being crushed by the justice system

The system costs far too much in money and in lives derailed without making us safer, she says

Since 1991, the number of children with a mother in prison has more than doubled

Former Secretary of State Hillary Clinton is a candidate for the Democratic nomination for president. The opinions expressed in this commentary are hers.

(CNN) When Tanya was 20, she made a new friend on the basketball court. For two months, they rode his motorcycle all over town, just hanging out. Then one day, he told her he needed to pick something up from his sister. He actually went and robbed a house. When the police caught up with them, Tanya was arrested. She was sentenced to 12 years in prison for a robbery she didn't commit.

Hillary Clinton

Alice grew up in a home scarred by domestic violence, though at the time she didn't know that's what it was called. She got pregnant at 15, and wound up in an abusive relationship herself. She ran afoul of the law and when she went to prison, her daughters were 10 and 2 years old. For 17 years, she missed every birthday, every graduation, while her children moved from family member to family member.

Mass incarceration has torn families apart, impoverished communities, and kept too many Americans from living up to their God-given potential. But mass incarceration's impact on women and their families has been particularly acute — and it doesn't get the attention it deserves. I learned about Alice and Tanya's experiences through a nonprofit organization that works with women in the justice system. (Both women's names have been changed to protect their privacy.)

Mass incarceration has torn families apart, impoverished communities, and kept too many Americans from living up to their God-given potential. Hillary Clinton

But women aren't the only ones affected when they are sent to prison. The high number of women in prison — and the long lengths of their sentences — destabilizes families and communities, especially their children. Since 1991, the number of children with a mother in prison has more than doubled . Mothers in prison are five times more likely than fathers in prison to have to put their children in foster care while they serve their sentences.

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