Thanks for the feedback!
The basic idea of the game is to solve the murder case. You discover this case, as well as evidence and the suspects by investigating the cards. Unfortunately I didn't manage to give full feedback on which cards can be investigated etc, but the basic idea is if a card appears when it is investigated then you could investigate that card. There is no penalty for doing it wrong. This is done by pressing the investigate UI button and then pressing on a card.
On top of this you have to question the suspects about the evidence, but you can question other people about other things. For example, questioning the rookie about the suspects gives you additional information on each of them that you can question the suspects on and so on. Again there is no penalty for questioning people about things, and the only way to tell if they can be questioned about a thing in the jam build if it results in a card. This is done by pressing the question UI button and pressing from a person to another card.
Finally to complete the game you have to accuse suspects of a crime using the accuse UI mode. To do this you press from a person to a crime (the card will be named "Crime:...") and then to a piece of evidence. This may result in a card appearing, if the card is a statement card admitting guilt then you have solved that crime. You win when you investigate the card resulting from the statement admitting the murder.
I hope this helps. And thank you for playing the game!
Also, if you could try to quantify what you were trying to do and what you found difficult it would be much appreciated