Sean Penn is an actor that has not done particularly well in my reviews so far. What I usually do not like of his performances is a tendency to overact, as well as to give what seem to be overly calculated performances that spend far too much time on mannerisms that get in the way of any actual characterization. These problems perhaps developed overtime because they will not be found in this performance.
Sean Penn's performance this is still certianly a very specific character. He uses an accent, as well as distinct way he stands and looks that suggests the upbringing as well as the past of his character. The reason they work in this film is because Penn is consist with them, and never puts an overt emphasis, rather simply having them there as part of the actual person that is Matthew Poncelet.
The other reason these mannerisms work in the performance is because he brings them in with a full characterization of the person, that is never just an an external attitude, but a person as a whole. Penn performance as Matthew Poncelet most certainly is careful and finely attuned but it still always remains natural, and his acting never becomes obvious as it does in some of his later performances.
Sean Penn's performance is quite interesting in how he shows the way Poncelet has almost developed himself into particular way from his life on death role. When the Sister Helen Prejean (Susan Sarandon) first comes to meet him, he attempts to act tougher than he really is. Penn is on the mark in creating a bit of a facade Matthew has, that he almost has to have, well still suggesting his actual more sensitive self.
I think something rather interesting that Penn does in this performance is the fact that he does not try to portray Poncelet as all that intelligent, but still not a simple man. Penn portrays his lack of intelligence actually in Poncelet's television interview where he makes several extreme remarks involving racism as well as terrorism.
Penn makes this seem as something Poncelet does not necessarily that he really at all believes it but rather he just again uses as some sort of attempt to show his anger over his condemnation. When questioned by the sister, Penn really shows just the complete lack of though Poncelet really has over the matter, Penn shows that Poncelet honestly is just not a smart man.
The most important part of his performance is of course Poncelet's whole relationship with the sister. Sarandon and Penn do wonders together, in creating the incredible unique relationship between the Nun and the death row inmate. It is fascinating because Sarandon portrays the sister always as warm, and loving, but still she pressures Matthew on his refusal to accept that he was at all guilty.
Penn though interestingly does not always show as much focus in the relationship until near the end, because Penn does a great job in showing that Matthew has a lot more on his mind all the time, and how his impending death, as well as his guilt is constantly eating away at him, making him more reluctant to try to always instantly accept the sister's method of try to save him.
Penn though eases in perfectly when they become more relaxed with one another, and begins to shed his facade of sorts, and really opens up to her, showing with Penn presenting Matthew's deep sadness and fear he deeply has inside himself. They eventually create a credible, very authentic relationship honestly based on very real platonic love for one another.
The most powerful moments of his performance are on his execution date. Every scene on his last day is made heartbreaking becuase through the entire ordeal Penn never strikes a single false note. From his last visit from his family, which is particularly effective because of how warm he is with his brother and his mother, as he tries to ignore the execution on his mind. To later nearer to it when he finally comes to grip completely with his situation and his guilt.
The final scenes are rather difficult to watch, because Penn really shows this being a human being killed, not some animal, but a man. A man with his honest fear of death, and finally his admittance of what he did. Penn never for a moment seems to be acting, he really becomes a man who is about to be killed, it is incredible as well as distressing to watch. This is simply a great performance by Penn that leaves an almost unforgettable impression.