By lan Finder

In the end, the prosecution of the four police officers reportedly indicted Thursday in the shooting of Amadou Diallo will rest on a deceptively simple question: when does a mistake become a crime?

New York State law permits police officers to use deadly force, but only under certain conditions. If an officer « reasonably believes » that his life or other people's lives are in danger, he is justified in using his gun.

So prosecutors will have to convince a jury or a judge that the four officers should be convicted because it was unreasonable for them to believe they were in danger. In addition, if the officers face second-degree murder charges, the prosecutors will have to prove either that the officers intended to kill Diallo or that their actions were so reckless that they demonstrated a depraved indifference to human life.

Second-degree murder is defined as the intentional killing of a person or a killing resulting from depraved indifference to life, and it is punishable by 25 years to life in prison.

« Crime is an intention and an act," said Jerome H. Skolnick, co-chairman of the Center for Research on Crime and Justice at New York University Law School. "The act is here. They shot this guy. So the whole thing will revolve around this: What was their state of mind? Did they have an objectively reasonable belief that their lives were in danger?

« A mistake is an excuse in legal terms, » Skolnick said. « If an excuse is believable, then you are excused of culpability. You are acquitted. »

« Their defense has got to be that what they did was justified, that they had a reasonable belief, given all the circumstances, that he was going for a weapon, » he said. A judge or jury « will believe them or not. »

Several of the lawyers representing the four police officers have already suggested that the officers thought Diallo was reaching for a weapon, although in fact he was unarmed.

But the Bronx grand jury that reportedly voted to indict the officers was unlikely to have heard much testimony about their state of mind. On the advice of their lawyers, the officers did not testify before the grand jury.

A New York City prosecutor who is not involved in the Diallo case said the grand jury could have decided that the firing of 41 shots by the police officers was itself a sign of recklessness, the kind of action that would elevate a mistake into a criminal act.

« I know this sounds simple, but legally it can be very difficult, » said the prosecutor, who spoke on the condition of anonymity. « If you engage recklessly in conduct that leads to a loss of human life, that can show depraved indifference to the human life. And that can be a theory for a charge of second-degree murder. »

But whether that theory will be upheld in a trial depends on many things. Will the officers testify? Will a jury or a judge find their testimony credible? Will other witnesses offer evidence that supports or undercuts the officers' contention that they reasonably believed they were in mortal danger? Will the prosecutors convince a judge or jury that the officers' actions were reckless enough to convict them?

And, perhaps most important, will the evidence support the standard for conviction: beyond a reasonable doubt? The standard for a grand jury to indict – that the evidence is « legally sufficient » to establish that the defendants may have committed the offense – is much lower than the standard for a conviction.

At the end of a trial, if a judge or jury considers the evidence insufficient to convict the officers of second-degree murder, they might have other choices, perhaps convicting them on lesser charges, like manslaughter. It was not clear last night whether any of the four officers had been indicted on any lesser charges.

Under New York State law, a defendant can be found guilty of the next most serious charge, first-degree manslaughter, if a jury decides he intended to cause the victim serious injury, but instead killed him. A defendant can be found guilty of second-degree manslaughter if a jury determines that he recklessly caused the death of another person, but had not intended to do so.

« If this had been my case, I probably would be charging at the high end – murder two – but it could have been that or manslaughter, » said the prosecutor, who is not involved in the Diallo case, but who has prosecuted police officers in other cases.

Skolnick of N.Y.U. Law School said the outcome of this case, like all cases, will depend on which side presents the more compelling argument. « All this is a narrative, a story, and the narrative has to be a convincing story, » he said. « Every legal case is a narrative. »