On Monday, the sentencing process for the shooter who murdered 17 people at Marjory Stoneman Douglas High School in Parkland, Florida, more than four years ago will start.

The jury will now decide whether Nikolas Cruz, 23, will receive a life sentence in prison or the death penalty. He has already pleaded guilty to each allegation.

While the prosecution is requesting the death penalty, Cruz’s defense team is advocating for the only alternative possible sentence, life in prison without the chance of release. (In Florida, parolees serving life sentences are not eligible.)

The trial, which is anticipated to last months, will feature testimony from witnesses and an assessment of the evidence by a jury of seven men and five women. The jury’s decision to execute a defendant must be unanimous. Cruz will be given a life sentence unless one juror changes their mind.