Discussion - Are muderers with a mental abnormality any less responsible for the murder?

Given that they had a mental abnormality at the time of the murder which lead to an impairment of judgement, irrational thinking and behaviour, impulsiveness, the inability to inhibit those impulses and the inability to comprehend the true nature of the action etc.

What do you believe about murderers with a mental abnormality being less responsible than/just as accountable as the 'ordinary man' for murderer?

I'm carrying out a project on this topic and as part of it I am seeking some public opinion. Ideas I wanted to explore encompass the notion of free will and determinism; such as the arguement there will always be a part of our brain that makes us do what we do because brain controls all behaviour. Therefore, does this make all people equally responsible for their actions? or even irresponsible if we have no control over our physiological stuctures? i.e. the brain.  E.g. one with a mental abnormality committed murder due to frontal lobe dysfunction of the brain and an ordinary man commited murder due to a normal functioning brain.

Anything else you can think of would be great. The question is: Are murderers with a mental abnormality any less responsible for the murder?

Please share YOUR views! not just the views of the law,

Thank you