According to an article published by the Wall Street Journal on March 24, 2015, a House Appropriations Committee hearing was held on Monday, March 23, at which two Supreme Court Justices gave testimony.
US Supreme Court Justice Anthony Kennedy made the following comment during a hearing to discuss the Supreme Court's annual budget request:
"This idea of total incarceration just isn't working." He added that it would be wiser to assign offenders to probation and other supervised release programs.
More importantly, US Supreme Court Justice Stephen Breyer testified that mandatory minimum sentences for specific crimes was a "terrible idea" and challenged Congress to "prioritize" improvements to the criminal-justice system.
While Justice Kennedy "usually sides with law enforcement in criminal procedure cases", he apparently holds the opinion that prison overcrowding can "violate the the Eighth Amendment prohibition of 'cruel and unusual punishments.'"