Not quite – there are three conditions needed for a sin to qualify as mortal. One of them is that the person give consent.
If by consent you mean deliberation, that is not quite true (though it is normally required). If I am suddenly enraged at the person sitting next to me such that I rise up and kill him, then I have not deliberated but ought to have been able to prevent such a thing to the point where I would not be free of mortal sin.
If by consent you mean an act of the will (by commission or omission), then it is true for any sin (or else it’s called “violence” and one is not culpable). If an assassin grabs my hand, puts it on the trigger, and pulls, I am not guilty of murder.
If by consent you mean that the intellect is involved sufficiently in the decision to do some act that is contrary to the commandments, then that’s true.
Our intellect is our ordering principle. It determines the “direction” or “orientation” of our existence. When infused with the graces of faith, hope, and especially charity, our existence is basically ordered toward God as its supernatural last end (or “ultimate purpose”). When we do something contrary to charity (which is the virtue that makes us a friend of God), we lose that grace of charity… We have chosen something that directly violates the “rules of the friendship,” so to speak, and if we did so with that ordering principle, the intellect, we have completely turned away from God making something else the last end of our existence. In death, we are given what we want: God, or not God.
All mortal sins are violations of charity and are contrary to the commandments.