McKing does not let you into the evidence room.
He is so damn perfect. And sends you to get him some coffee.
From the coffee machine, yes. And he will drink all the coffee you get him.
Maybe you could spice the coffee up for him. Maybe he would like to visit the toilets...
There's laxatives in the first aid kit near the reception. Mix the laxatives into a coffee from the coffee machine and give the coffee to him to make him visit the toilets.