To earn the "NOTHING TO SEE HERE" trophy in Detroit: Become human, you must complete the chapter "MIDNIGHT TRAIN" having successfully convinced the police officer to go away. This is a Kara chapter so Kara must have survived the events of chapter "ZLATKO", you can find a guide for that here:
Once Rose has left the house you should speak to Adam and reassure him. I went for honesty. When the policeman knocks, close the door leading to the grieving deviant, tell Luther to take Alice upstairs and shut the cabinet under the stairs. I believe there is more you can hide but the timescale is tight, and I didn't find it necessary to succeed.
When the officer comes in, you need to make sure your story is consistent. Make him a coffee. When he asks if anyone else lives here, you should tell him about Alice. When he asks if you have any androids, you should say yes; in my playthrough he found an android jacket but your explanation means his suspicions are not overly raised, and when he hears a noise upstairs you've already primed him with an explanation by saying Alice was upstairs. When he questions Adam, you should interrupt and say Adam is tired. Adam shouldn't give you away if you took the time to reassure him. On the way out of the door the officer hears a noise from the room with the grieving android. Tell him it's the washing machine and he will buy it.
Soon after the chapter will end and you should receive the trophy in the flowchart screen.