Well first you have to eliminate necessity and chance as possible causes of what you are investigating.
The criteria for inferring design in biology is, as Michael J. Behe, Professor of Biochemistry at Leheigh University, puts it in his book Darwin ' s Black Box: "Our ability to be confident of the design of the cilium or intracellular transport rests on the same principles to be confident of the design of anything: the ordering of separate components to achieve an identifiable function that depends sharply on the components.”
That is the positive case.
We do not need to know who the designer was to do any of that.
What good is a design inference? For one it tells us that necessity and chance were not up to the task. It tells us that some agency was responsible and therefor any causal story of the object/ structure/ event has to reference that fact. And guess what? It matters to any investigation how what is being investigated came to be the way it is.
IDists have determined that living organisms are designed because they meet the above criteria. IDists have determined the subsystems inside of living organisms are designed because they meet the above criteria.
Heck the anti-ID assholes don't even have a methodology to determine if blind and unguided processes can produce a living organism nor the subsystems. So what do they do? Attack ID with their ignorant spewage and lies.
For example Kevin McCarthy is full of ignorance and lies- read it for yourself- every "point" he tries to make has been answered. But Kevin will never know because he chooses to be willfully ignorant- Yes, You Must Have a Designer
Strange that when all it takes to get rid of ID is to actually stand up and present positive evidence for blind and unguided processes we get bullshit ignorance instead.
Look Kevin, attacking ID will NEVER produce positive evidence for your lame position. Never.
The design inference is based on our knowledge of cause and effect relationships. For centuries that knowledge has helped us detect design in the absence of a designer.
So to sum it all up- Yes we have detected design in living organisms, living organisms themselves and in the universe. OTOH dickheads like Kevin don't even have a methodology for testing the claims of their position. They are totally ignorant of science- they must be to be in their position thinking that sheer dumb luck is a scientific PoV.