The Court has set the penalty phase of the trial of Boston Marathon Bomber, Dzhokhar Tsarnaev, to begin on April 21, 2015, the day after this year’s Marathon Monday.

Because this is a federal death penalty case, the trial is broken up into two parts. First the jury had to determine if Tsarnaev is guilty of any of the 17 out of 30 charges against him that carried a possible death sentence. If the jury found that Tsarnaev was guilty of any one of those 17, they would then move into the penalty phase, to determine whether he should be sentenced to life in prison without the possibility of parole or to death. Here, the jury found Tsarnaev guilty of every charge against him.

During the penalty phase, the jury will consider aggravating and mitigating factors. Aggravating factors are things that make the crime worse, like premeditation or that there were multiple victims. Mitigating factors are things that lessen the gravity of the crime, like the lack of a defendant’s prior record or if a defendant was acting under duress.

Federal statutes control the procedure that the jury must follow in weighing the aggravating factors against the mitigating factors and the mandates of those statutes are more complicated than you may think.

Here’s how it works.

The Aggravating Factors:

The government will present its evidence first.

Federal statutes provide a list of aggravating factors that a jury must consider after a defendant is found guilty of a crime that carries a possible death sentence. The government is required to prove at least one of those aggravating factors BEYOND A REASONABLE DOUBT before a defendant can be sentenced to death. A finding of an aggravating factor must be UNANIMOUS among the jurors.

Like in all federal death penalty cases, here, the government was required to file a Notice of Intent well in advance of a guilty verdict, declaring its intention to seek the death penalty and spelling out exactly what aggravating factors it plans to prove to support a death sentence. According to the Notice of Intent filed on January 30, 2014, the government intends to establish the following statutory aggravating factors:

  • death during the commission of another crime;
  • grave risk of death to additional persons;
  • heinous, cruel and depraved manner of committing the offense;
  • substantial planning and premeditation;
  • multiple killings; and
  • vulnerable victim (which speaks specifically to the death of Martin Richard, an 8 year old boy).

Remember, the government needs to prove at least one of these listed statutory aggravating factors, beyond a reasonable doubt as unanimously determined by the jury, before a death sentence can be imposed. This will be relatively easy because some of these factors have already been determined by the jury in the first phase of the trial.

If one of the statutory aggravating factors is found to exist, the jury may also consider other aggravating factors, so long as the government has outlined them in its Notice of Intent. Here, the government will ask the jury to also consider the following non-statutory aggravating factors:

  • betrayal of the United States;
  • encouragement of others to commit acts of violence and terrorism;
  • the impact on the victims and their families;
  • the selection of the iconic Boston Marathon site for Acts of Terrorism;
  • lack of remorse;
  • status of victim (which relates specifically to the status of Sean Collier, as a law enforcement officer who was engaged in his official duties at the time of his death); and
  • participation in additional uncharged crimes of violence (including assault with a dangerous weapon, assault with intent to maim, mayhem, and attempted murder).

It is likely that the government will make its case through testimony by the victims and their families.

The Mitigating Factors:

Once the government is through with its presentation of the aggravating factors, Tsarnaev’s defense team will present the mitigating factors.

The burden of proof on the defense is much less onerous than that on the government. Like with aggravating factors, the federal statutes prescribe a list of mitigating factors but included in that list is a broad category called “other factors” which basically means that the jury can deem almost anything a mitigating factor.

The defense is only required to prove a mitigating factor BY A PREPONDERANCE OF THE EVIDENCE, which means that it is more likely true than not true. Moreover, a finding of a mitigating factor only needs to be made by ONE JUROR to be deemed a mitigating factor.

This means that a juror can consider any mitigating factor that he/she determines is more likely true than not, while he/she may only consider the aggravating factors that are proven beyond a reasonable doubt

and accepted by all jurors unanimously. This is a testament to the fact that the death penalty is reserved for the most heinous and unforgivable crimes.

It is likely that the defense will try to show that Tsarnaev’s older brother, Tamerlan, was the mastermind and that Tsarnaev was only following orders. The defense may also argue that Tsarnaev’s age (he was 19 during the commission of the crimes) and family history are mitigating factors. Most of this evidence will probably be presented through expert testimony. It will be interesting to see if Tsarnaev takes the stand to plead for his life.

Weighing the factors:

After both sides present their evidence the jury must consider whether the aggravating factors found (unanimously and beyond a reasonable doubt) outweigh the mitigating factors to justify a sentence of death. The jury has to come to a UNANIMOUS vote for a death sentence.

This is a federal case being decided by jurors from Massachusetts, a state that does not have the death penalty. Whether Tsarnaev will be sentenced to death is difficult to predict.