Karlheinz Böhm did not receive an Oscar nomination for portraying Mark Lewis in Peeping Tom.
Peeping Tom was an extremely controversial film upon its initial release to the point that it severely damaged director Michael Powell's reputation, and the film itself was almost lost to obscurity due to this reaction. It is interesting to compare the reaction of this film to that of Psycho which came out the very same year. Although the film developed from similair pedigree in terms of filmmakers, and both did incur some controversy, Psycho though still found mainstream success while Peeping Tom did not. Both films are about psychotic killers, we see the murder scenes with detail, but there is one major difference with Peeping Tom. In Psycho we are not made aware of who the killer is until the end in addition there are pseudo alternative protagonists to follow. In Peeping Tom the killer is the protagonist and we know this from the opening scene where we watch him slowly murder a prostitute. Powell ensures we are part of the murder so to speak as we view the murder directly through the killer's camera.
Karlheinz Böhm plays the psychotic killer Mark who curiously we are not meant to fear exactly, at least not in the normal way. Böhm's performance has the qualities you might expect from such a character. He is chilling in the murder scenes where he portrays the method in which Mark goes about his murder. Böhm's approach though is rather disturbing by showing a specific fascination in Mark in these moments. He's detached yet he's also not. Böhm portrays that Mark is captivated in the moment, yet he still goes about the murder itself without any hesitation. Böhm is chilling by realizing this curious mindset in Mark, which is that he is almost too deeply entranced in the act of observation which leads him to commit these murders in such a peculiar way. The nature of the murder scenes though are not from a thriller, and Böhm's performance is not that of a villain in a thriller. There are policemen after him, who we occasionally see, yet the intention of the film is to examine the voyeur as a man rather than examine how he is caught.
This intent in the film likely encouraged the controversy since the film does not desire that you hate Mark. Powell's direction along with Böhm's performance, even though we know from his first scene that he is a coldblooded killer, does challenge the viewer to sympathize with Mark throughout the film. Now this is not in the sense of seeing how he gets away with acts of violence, but rather sympathize with his mindset. Böhm plays Mark as a shy introvert and conveys almost this degree of naivety to the man. There is an earnestness that Böhm brings to his behavior, even though he is hiding a much darker side, somehow elicits this certain element of likability to Mark. In the scenes where Mark interacts with his neighbor Helen (Anna Massey) Böhm brings a charm almost in his awkwardness, as Mark struggles to make a good impression. Böhm does not play this as a serial killer who is trying to hide himself, but rather actually as a normal man attempting to honestly communicate best he can.
It is revealed that Mark's world view was indirectly encouraged by his own father who used him as for his own scientific studies, which he always documented with a camera. Böhm utilizes the backstory in his performance as he manages to give understanding to Mark's motivation as twisted as it may be. The damaged nature of Mark is made to be a constant in Böhm's work. In the moments where he speaks of his past Böhm reveals this off-putting attachment to it. Böhm speaks as though Mark is unable to escape what exactly the treatment had done to him, and leaves him in the painful state he is in. Böhm once again never brings a viciousness to Mark as the killer, he rather portrays his murders as a side effect of his affliction. Böhm shows there to be an irresistible urge in Mark as he goes about his behavior, never revealing a real pleasure in it. In fact when the urge begins to reveal itself around Helen, Böhm effectively reveals a real distress in Mark as he attempts to fight against that urge. Now the portrayal of the urge in itself is the most unnerving element in the film, because Böhm creates this fascination in Mark in the act of observing itself, not unlike someone watching a captivating film of any sort. Böhm's work captures the idea of that emphasizing with what he is watching though twisted into the depraved act of killing. It's a striking performance as Böhm allows one to understand Mark's demented mind and through that, along with Michael Powell's imagery forces the viewer to become invested in a most questionable man.