Daniel Penny, who put the man, Jordan Neely, in a chokehold last year, told investigators that Mr. Neely posed a deadly threat. The killing polarized New York.

The Manhattan DA’s office declined to comment on their legal strategy for trial. One of Penny’s attorneys, Steve Raiser, said in a text message that their case will focus on the government’s failure to address mental health and homelessness on the subway.

On Monday, lawyers on each side of the case began presenting questions to potential jurors, like if they had heard of the case before. Jury selection will be tedious, as will the rest of the trial, Nicole Brenecki,