All the science and analysis and consideration for the trajectory of all things spherical is good on paper, and complex
However the over riding factor is simple. Do you as referee deem what you see to be deliberate. If do, penalise it. If not, and I would suggest without inside knowledge of Opta, nine times out of ten, I would consider handball not to bd deliberate. I mean, who at the top level of football, on 100k per week, having trained pro for 10 years, really gives away a pk to their opponents by putting their hand onto the ball?
Defender is aware a cross is going to come in, and thinks, hey, am well aware if I use my hand to block this I will conceed a pen but fcuk it, I will do it anyway?