Killing with bare hands vs Rube Goldberg killing machine: How can we connect causes to persons, and so be morally responsible for effects by us?

Question

What brought up this question:

• I was watching a television show and was thinking of how powerful individuals can obtain hired guns to do their dirty work. The police and legal system then has difficulty arresting the person who set the crimes in motion.

Expanding on the question:

• I believe the example and hypothetical of killing with bare hands vs a rube goldberg killing machine is very useful here.
• To take it to the extreme as another example, what is the reasoning for political leaders being responsible for decisions they make. Mao Zedong and Hitler may not work since they actually personally did immoral things. I am thinking, say, current US president Joe Biden (a reasonably moral person far from literal evil) being jailed years later for a key decision on climate change that somehow led to deaths. (But climate change might be a bad example, since that is partially a collective problem)
• Perhaps it need not be illegal and immoral effects, it can be about prosperous as well. Nor need it specifically be about persons. How can we reasonably pin a phenomena for being the true or primary cause for something? Such a constraint relaxation helps so that concepts from philosophy of science or metaphysics might be able to lend something here.
• I suppose my issue is just understanding how anything other than doing things directly with your own personal hands and body is reasoned to be caused by you. A related matter might be the various thought done on how technology and tools are extensions of the mind and body (whereby language is also a shared 'tool').
• I'm giving a lot of examples, but only because I am trying to exemplify the question. That's not really the focus the answers should have though. I was curious about the philosophy and reasoning behind the question.

What this question is not focused on:

• The psychology, or biology, of moral responsbility to the degree that we are in control of our actions. Such as the mentally ill, etc.
• Current laws or legal theory. As we learned 2000+ years ago, what is popular or instantiated in society is not necessarily what is true.

Answer 1

actus reus or the physical act

Cause is never measured, only modeled. We can measure "Alice is stabbing Bob" and we can subsequently measure "Bob has stab wounds to his vital organs and is dead", but the statement "Alice killed Bob" is inferred using a model: "stabbing usually causes stab wounds, stab wounds are seldom caused by things other than stabbing, and stab wounds of the vital organs usually causes death". Cause is determined by assessing the predictive effectiveness of the model (how well experiment favors the model over the null hypothesis) and the measurements of initial and end conditions.

If we measure Alice stabbing Bob, but then we measure Bob alive afterwards for several days, and then we measure Bob being run over by a truck driven by Charlie, we don't conclude that Alice killed Bob, because the end conditions don't match the model. If we measure Alice minding her own business, and then we find Bob dead with stab wounds, we don't conclude that Alice killed Bob, because the initial conditions don't match the model. If we measure Alice tickling Bob, and then we find Bob dead of an unknown cause, we don't conclude that Alice killed Bob, because experiment strongly favors the null hypothesis over the model "tickling causes death".

If we measure Alice hiring Charlie to run over Bob with a truck (or evidence which allows us to infer that she did so), and we measure Bob lying dead under a truck driven by Charlie later, and "hiring people to run over other people with trucks often causes death" is a model which experiment strongly favors over the null hypothesis, we conclude that Alice and Charlie killed Bob.

mens rea or guilty intent

Moral responsibility is generally assessed in based on whether the guilty party knew or should have known what the consequences of their actions would be. If Alice tells Charlie "Charlie, if you run over Bob with your truck so that he dies, I will give you $1000," then Alice and Charlie are guilty. If Alice tells Bob "Go get run over by a truck, asshole!" and Charlie overhears and decides to run over Bob, then Alice is innocent and Charlie is guilty. If Alice superglues an unloaded gun to Bob's hands and runs screaming past Charlie's truck saying "Bob is trying to shoot me, run him over!" then Alice is guilty and Charlie is innocent (or has lawful use of force as an affirmative defense).