When it debuted, California's three-strikes-and-you're-out sentencing law represented the toughest - and most controversial - crackdown on criminals in modern history.
Forty states since then have adopted similar measures, which lock up defendants for life after their third felony conviction, often crowding court dockets and prisons in the process.
Now, though, the three- strikes law faces what may be its biggest test since voters approved it seven years ago. For the first time, a US appeals court has struck down a long sentence imposed under the law, saying it amounts to cruel and unusual punishment. The ruling is already igniting debate over the merits of strict mandatory sentences.
"This finding has put the future of three-strikes laws in limbo," says Robert Pugsley, a constitutional scholar at southwestern School of Law, Los Angeles.
"Whichever way this ends up going," says Mr. Pugsley, "will either reinforce the tendency of other states to overcriminalize [third-strike felonies] and oversentence them, or give [the states] a warning they can't do that anymore."
While the ruling by a panel of three judges did not invalidate the California law, the case may yet wind its way up to the US Supreme Court and make other judges more reluctant to hand down sentences that may later be appealed.
The ruling may also unleash a wave of appeals from the estimated 350 to 3,500 other California prisoners who received comparable sentences in similar circumstances.
"It's going to lead to many challenges by those currently in prison whose third strikes were also minor crimes," says Erwin Chemerinsky, a constitutional-law scholar at the University of Southern California and the lawyer who represented the defendant in this case, Leandro Andrade.
Mr. Andrade stole videos worth $153.54 from two K-marts and wound up with a sentence of 50 years in prison with no possibility of parole.