If lethal force is justified, officers are taught to keep shooting until the threat is over. Plumhoff v Rickard 2013

Police officers are often forced to make split second judgments in circumstances that are tense, uncertain and rapidly evolving. Graham v Conner 1989

Where an officer has probable cause to believe that the suspect poses a threat of serious physical harm, either to the officer or to others, it is not constitutionally unreasonable to prevent escape by using deadly force.  Tennessee v Garner 1985

These are important quotes from three U.S. Supreme Court cases that address alleged police brutality, and they outline how courts determine whether the use of force is excessive. As such, they have a direct bearing on recent events in Ferguson, Mo., and the case involving a police officer, Darren Wilson, who shot and killed an unarmed African-American named Michael Brown.

Given that many are calling for murder charges to be brought against the officer, it is probably fair to say this matter will ultimately end up in court. In the meantime, people have taken to the streets in protests over Brown's death. They cry for justice. But, under our legal system, justice is meant to be served within the confines of the system and not on the streets. Our legal system has addressed cases surrounding the use of police force as recently as last year, and these serve as a guide for what may happen in this one.

Under the law, it is very difficult to bring criminal charges against a police officer when he or she commits an allegedly criminal act while in the line of duty. It is unlikely that Wilson will be charged with either murder or committing a hate crime. To do so, the prosecution must prove malicious intent, which is a difficult burden to overcome. Here the prosecution would have to prove beyond a reasonable doubt that Wilson intended to murder Brown. While that remains the consensus among many who protest, there is no evidence of such intent thus far. In fact, we know very little about the officer's side of the story other than that he alleges he was assaulted, and there has been some indication he was injured. If this is true, the chances of murder or hate crime charges become miniscule.

If that becomes the outcome, Michael Brown's family could sue the officer and the police department for monetary damages, including punitive damages, under federal law. Title 42 U.S. Section 1983 allows citizens to bring cases against the government when they have been deprived of their constitutional rights. As Brown was deprived of his life, his family most certainly has a case on his behalf. If such a case is filed, most likely a jury (and not a judge) will have to determine whether the officer used reasonable or excessive force.  

The Supreme Court has established some circumstances in which deadly force is reasonable. In the case of Tennessee v Garner, the Supreme Court said the key questions are:

1. Has the officer been threatened with a deadly weapon?

2. Does the officer have probable cause to believe the suspect poses the threat of serious physical harm or death to the officer or another?

3. Does the officer have probable cause to believe the suspected committed a crime involving actual or threatened serious physical harm or death?

Before jury members can determine whether the officer's force against Brown was reasonable, they will need evidence to help them answer these questions:  Did Brown threaten the officer involved? Did the officer reasonably believe that there was a threat of harm? And did the officer have probable cause to believe a serious crime had been committed?  

If we go solely by witness statements heard thus far, the answer to all of these questions is no. But it cannot be a "he said-he said" case until we hear from the other side.

Unfortunately, the police have not provided many details about their side of the story because, the police claim, they want to protect the integrity of the investigation. We might not agree with this explanation, but until we have both sides of the story, we cannot attempt to answer the questions a jury will ultimately have to review.

One thing is certain: There will be an investigation. Evidence will be collected, and each side will have the opportunity to argue its case. This is the way our system works, and we must give it the time and opportunity to do so.  

Ultimately - as in so many of these cases - the outcome will boil down to what is reasonable. To that point, the actions of the Ferguson police since Brown's shooting have demonstrated little to support the idea that they respond to threat reasonably. That may cost them when it comes time for a jury to pass judgment on them and the officer in question. But any attempt to try this case in the streets, in the media or on Twitter is neither fair nor helpful.

Justice takes time and patience and is best rendered in a court of law. Thomas Jefferson said, "No man is above the law and no man is below it; nor do we ask any man's permission when we ask him to obey it."

In our legal system, both Brown and Wilson stand equal before the law. If we give our legal system time to do its job, justice will be served.  

Heather Hansen is a partner in the O'Brien and Ryan law firm who has been named one of the 50 top female lawyers in the state by Pennsylvania Super Lawyers. Heatheris also anational television and radio legal analyst and journalist who has appeared extensively on CBS News, Fox News, Fox Business Channel, Fox.com, CNN, HLN and Sirius XM radio. Her writing has appeared in Law360 and she has co-authored two chapters in medical texts regarding medical malpractice litigation. Follow her on Twitter at @imheatherhansen.