Two years after approving a tough-on-crime sentencing law, South Dakota is scrambling to deal with the price tag for that legislation: Housing thousands of additional inmates could require up to $2 billion to build new prisons in the next decade. “Crime has been falling everywhere in the country, with historic drops in crime in the last year or two,” said Bob Libal, senior campaign strategist at the criminal justice nonprofit The Sentencing Project. For now, state lawmakers have set aside a $600 million fund to replace the overcrowded 144-year-old South Dakota State Penitentiary in Sioux Falls, making it one of the most expensive taxpayer-funded projects in South Dakota history.