Actually in the first episode they make a direct statement that crying is ok. A female police officer apologized for crying as she was explaining something she had witnessed. And a male officer comforted her by saying he crys all the time, and makes a joke to diffuse her insecurities around it.
Because it depicts the gruesome murders of Jack the Ripper, there is specific graphic things it shows. Including body innards. For what it's showing, it's toned down, minimal blood considering the extent of the crime. But the bodies are a big part of the story, and there are many close up scenes showing corpses cut up & cut open, parts taken out, etc.
At about 35 minutes in, Joe gags a lot and vomits when he goes down into the sewers and dirty water pours onto him. He gags quite a lot throughout the show too.
S1:E3- end of episode - talked that someone may take their life and they are seen floating down deeper in the water. S2:E3- another suicide Stopped watching show so not sure if there are other scenes.
Would say moderate levels of flashing and flickering included in every episode. During the opening sequence, and some transitions. They periodically flicker images of the past case along with some lights to give the somewhat haunting ambience. There's also flash photography when they are at the recent crime scenes, and by reporters / paparazzi.