BOSTON — Federal prosecutors say they won’t try to prove Boston Marathon bombing suspect Dzhokhar Tsarnaev shot Massachusetts Bay Transportation Authority Officer Richard Donohue, but say he’s still responsible for the officer’s injuries.

In a federal court filing Friday, prosecutors said the government doesn’t intend to offer evidence that Tsarnaev shot Donohue.

Instead, the government alleges Tsarnaev is responsible for Donohue’s injuries because Donohue was shot while he and other officers were trying to prevent Tsarnaev’s escape.

Tsarnaev has pleaded not guilty to 30 federal charges in connection with last year’s attack, which killed three.

Investigators have never said who shot Donohue, who has said that he has no memory of the encounter on the streets of Watertown, Mass., between police and bombing suspects Tamerlan and Dzhokhar Tsarnaev.

Federal prosecutors are also asking attorneys for Tsarnaev to notify them if they plan to introduce any evidence that Tsarnaev suffered from a mental illness.

Prosecutors said the defense should disclose any such plans by May 7, a date previously set for pre-trial motions in the case.

The government said it was seeking notification of plans to present “expert evidence relating to a mental disease or defect or any other mental condition … which bears on either the issue of guilt or the issue of punishment.”