While in Detroit for the 2nd time, Pritchard will be in contact with you as you walk around and he'll inform you that you should go meet Brent Radford.
Head over to his apartment and head into the bedroom. Make sure you don't get caught by the guard and take him down. You'll now spot Brent dying on the floor in the bathroom. Strike a conversation with him and he'll ask you to find his medic pack. Agree and exit the bathroom. Look in the corner of the closet to your left as you exit and you'll see it on the floor.
Head back to Brent and administer a dose of morphine to him. Each time he asks for another does, apply some more. Once you have all the information you need, Brent will ask for one more dose to kill him. Don't worry this does not void the 'Pacifist' achievement, so go ahead and give him the last dose. Once he dies, the 'Kevorkian Complex' achievement will unlock.
After this carry on with the side mission. You'll now need to go to a lock up and find the last bit of evidence Brent informed you about. Make a save here then takedown the 3 guards outside without getting caught. Now read the 5 emails on the PC and look at the evidence in the safe. Now that you've searched the safe, do the follow up objective by seeing Michelle Walters and the achievement will unlock.