<P> Although sentences vary for each state, generally the life imprisonment sentences are mandatory sentences for first degree murder, particularly when the first degree murder is done during the commission of another felony (the felony murder rule), or there are other aggravating circumstances present (such as is common for rapes which precede such murders, or the first degree murder of any law enforcement official or other public servant) in all 50 states and the District of Columbia, including states without the death penalty, and as an (or the only) alternative sentence in states that have the death penalty and in federal and military courts . Life imprisonment is also a mandatory punishment in Idaho for aircraft hijacking, in New York for terrorism, in Florida for capital sexual battery (sexual abuse of a child under 12 years old that causes injury to the child) and in Georgia for a second conviction for armed robbery, kidnapping, or rape and other serious violent felonies under Georgia's Seven - deadly - sins law . </P> <P> Life imprisonment is a possible punishment for aggravated mayhem and torture in California . Other specifics about life sentences in the United States continue to vary widely by individual states . Also, it may be given for "drug kingpins" and "habitual criminals". It has been applied in every state except Alaska, as well as in the federal courts . In Alaska, the maximum term of imprisonment is for 99 years, although this is almost always considered to be a theoretical life sentence . </P> <P> Over 159,000 people were serving life sentences as of 2012, with just under a third--nearly 50,000--serving life without a chance of parole . In 1993 the Times survey found, about 20 percent of all lifers had no chance of parole . By 2004 the number rose to 28 percent . </P> <P> As a result, the U.S. is now housing by far the world's largest and most permanent population of prisoners who are guaranteed to die of old age behind bars . At the Louisiana State Penitentiary, for instance, more than 3,000 of the 5,100 prisoners are serving life with a chance of parole, and most of the remaining 2,100 are serving sentences so long that they cannot be completed in a typical lifetime . About 150 inmates have died there in the last five years . An article for QZ reported that 35% of all the world's prison lifers are in the U.S. </P>

How many prisoners in the us have life sentences