The first deadly encounter of 2011 came quickly for police in Los Angeles County, when an officer killed an armed burglar on the second day of the year. The last person to be killed by police that year was shot a few days after Christmas in Palos Verdes after he allegedly beat his elderly father and pretended to point a gun at officers.
Between these ill-fated bookends, 52 other people throughout the county were shot fatally by police throughout 2011 -- significantly more law enforcement killings than the county typically experiences. Compared with the prior year, the 54 deaths amounted to a nearly 70% increase.
The high number of killings last year underscores a pronounced jump in the overall number of occasions in which officers fired their weapons at suspects. For example, the 63 shootings by officers from the Los Angeles Police Department in 2011 were a nearly 60% increase over the previous year.
The rise in killings by police is all the more notable because it occurred at a time when the overall number of homicides in the area had fallen to historic lows. With 612 people killed in the county last year, nearly 1 in every 10 such deaths occurred at the hands of law enforcement officers.
The Times has analyzed autopsy reports from each of the 54 killings by police in L.A. County last year and identified elements that were common to many of them. The review also highlights the extreme, sudden dangers police can encounter in the field and may raise doubts about whether, in some instances, the officers were justified in their decision to open fire.
Among the findings:
* All but six of the fatal shootings involved officers from either the Los Angeles Police Department or the county's Sheriff Department, which, taken together, patrol the vast majority of the county's roughly 10 million people. The other six were committed by police in Long Beach, Downey and Santa Monica.
* In two-thirds of the cases, the person shot by police was armed with a gun, knife or other weapon, whereas in 12 cases, the person was unarmed. In the remaining few cases, it was not clear from the autopsy reports whether the person killed was armed.
* Eighteen of the shootings -- one-third of the total -- occurred when officers were dispatched to respond to a report of shots being fired, an armed suspect or an assault with a deadly weapon. In at least 12 of those cases, the person shot by police was armed with a gun, a knife or a realistic-looking replica of a gun. By contrast, 12 shootings were set in motion not with a call for help, but rather with an officer's choice to initiate contact with someone he believed was acting suspiciously. In seven of those cases, the person shot by police was armed with a weapon.
What, if anything, drove the increase in killings by law enforcement officers last year is not clear.
Michael Gennaco, who heads the county's Office of Independent Review, said he's in the midst of examining the unusually large number of fatal shootings by sheriff's deputies to decipher the jump. "Until you really pull each of them apart, you don't know whether it was just a blip or if it is the start of an upward trend," he said.
Some law enforcement officials and researchers, including LAPD Chief Charlie Beck, have speculated that as police refine strategies for identifying and patrolling crime hot spots, they have become more adept at responding quickly to violent situations that lead to shootings. Beck emphasized that most of the shootings by police involved armed suspects. "By and large these are not shootings of misperception or overreaction," he wrote in response to questions from The Times. "They are legitimate responses to serious threats."
So far this year, the rate of police shootings has fallen back to previous levels.
When training to become police, recruits spend scores of hours on firing ranges and in simulation exercises to prepare for the split-second decision they may have to make in the field of whether to shoot at a suspect. The vast majority end up going through their careers never firing their weapon, let alone hitting and killing a person.
Police are authorized to use deadly force only in certain situations. They may shoot to protect themselves or others from an immediate threat of death or serious injury, to prevent a crime that could lead imminently to someone being killed or injured, or to stop a violent felon from fleeing.
Officers who fire their weapons must be able to explain why, from their perspective, it was necessary to use deadly force.
Controversies often arise when it is not clear to the public or investigators that the officer's decision met the criteria for shooting.
The autopsy reports reviewed by The Times included investigators' accounts of the shootings. Many indicated strongly that the officer's use of deadly force was justified.
On a night in January, sheriff's deputies pulled over Nestor Torres, a known gang member, for driving erratically. Torres stepped out of the vehicle and fought with the deputies, shooting one of them in the face. The deputy's partner returned fire.
The autopsy showed that Torres had ingested cocaine, amphetamines, PCP and alcohol before the encounter, although it is not known how much his behavior was affected by the drugs. In all but five of the fatal shootings last year, the dead were found to have at least one drug in their systems.
In some cases, however, the decision to fire was less obvious.
In October, Downey police responded to an intersection where an armed man had been seen by a 911 caller. The officers spotted Michael Nida, 31, in the area and believed he matched the description the caller had given.
When the officers confronted Nida, he fled. They gave chase, and one of them shot Nida twice in the back with a rifle from about 20 feet away when he "made a gesture that was perceived as a threat," according to the autopsy report.
Nida was unarmed.