The jury of 7 women and five men convicted Dzhokhar Tsarnaev this afternoon on all 30  charges in the indictment. Next up will be penalty phase. Before sending the jury home this afternoon, Judge O’Toole ordered them to return tomorrow morning.

Before the jury reached its verdict, it sent out two questions seeking definitions of liability for accomplices and co-conspirator liability. This is not surprising because jurors often struggle with these concepts.

Under federal law, a person can be convicted of committing a crime (e.g., shooting Officer Sean Collier to death) even if they did not pull the trigger, if they aided and abetted the shooter to commit the crime. Aiding and abetting means acting with the specific intent of assisting another person to commit the crime. Another word for that liability is accomplice liability.

A second way to commit the crime is to be a member of a conspiracy. A conspiracy is an agreement between two or more people to commit a specific crime. The crime of conspiracy is completed when a member of the conspiracy commits an overt act in furtherance of the conspiracy. The overt act does not have to be an illegal act. Any act, regardless whether it is an illegal or legal act, can qualify as an overt act, if it was committed by a member of the conspiracy with intent to further the objective of the conspiracy. Each member of a conspiracy is guilty of all crimes committed by co-conspirators in furtherance of the conspiracy, even if they were not present when the crime was committed and did not know the crime had been committed. Presence at the scene of the crime when it is committed is sufficient to attach liability for committing the crime, so long as the crime was a reasonable foreseeable crime that some member of the conspiracy would commit.

While mere presence at the scene of a crime when it is committed is insufficient to convict someone, they are responsible legally if they were a member of the conspiracy and present to assist another member of the conspiracy to commit the crime.

This is why, for purposes of imposing liability for killing Collier, it did not matter who pulled the trigger.

Conspiracies often have multiple objective, so you have to look at the indictment to see what objectives were alleged.

Basically, the jury found that Dzhokhar and Tamerlan formed a conspiracy to commit acts of terrorism against the U.S. by, among other things, detonating two bombs near the finish line of the Boston Marathon and killing Officer Sean Collier aDzhokhar was convicted both as an aider and abettor and as a co-conspirator.

The indictment charged Dzhokhar as both an accomplice and as co-conspirator.

The identity of the person who pulled the trigger, as well as Dzhokhar’s relative involvement in the conspiracy are relevant factors to consider in deciding what sentence to impose.