Background: In Luther, Series 3, episode 1, Ken Barnaby is a suspect in the case of a murdered internet troll, Jared Cass. Cass had tormented Barnaby and his wife over social media after their daughter passed away.

When he knows he is about to be caught, Ken sticks his right hand in a blender, presumably to damage his fingers to avoid being convicted on the murder charge via a fingerprint match. His left hand was unscathed, yet he still believes that he will be exonerated.

Why wouldn't the police simply use his left hand to match the prints? Is this a nuance of British law that they did not elaborate on in the story, or just a plot device?

  • ...Please take a moment to compare the fingerprints on your left and right hand. Are they the same (or at least mirror images of each other)? I rather suspect the answer is "no". If Mr. Barnaby only left prints from his right hand, then the police would have a difficult time proving they belonged to him. Given people usually use their main hand for most tasks, this stands a decent chance of taking the source out of the picture (unfortunately for him, prints from his right hand are likely all over his own house....) Commented Jan 29, 2015 at 11:46
  • @Clockwork-Muse I'm not sure I buy that. It would be nearly impossible not to touch anything at all with the left hand. I agree that there would be a lower probability of being discovered, but why not injure both hands? In the States, people are usually fingerprinted with both hands, I'm wondering if it's different in the UK.
    – jonsca
    Commented Jan 30, 2015 at 0:24
  • Impossible not to touch something with your left hand, yes, but you'll use your right hand for more things, so investigators would be more likely to find right-hand prints (and more usable ones, too). I haven't seen the show at all, so I don't know what the police may have on him (or what he thinks the police have on him). Commented Jan 30, 2015 at 2:34

2 Answers 2


It might not be enough to exonerate him, but he doesn't have any other choice.

Point 1: British law in taking the prints

I can't remember where they find the fingerprint, but from the question I'm guessing it's an unidentified print in the victim's house.

The police had no reason to take his fingerprints before then because a. whilst he was a suspect, they had zero evidence against him, and b. they had found no fingerprints before then to identify his against.

This means they had no justification to take his prints before they found the print in the house.

Point 2: Only removing his right hand

When Luther phones Ken Barnaby, he knows from the phone call only that the police have found a single fingerprint, and that the police will be coming the next day to take his fingerprints to compare to.

Now, Ken Barnaby's state of mind is fragile. In a short space of time he has both lost his (only?) daughter and killed a man. Clearly he isn't thinking straight.

Now, Ken knows that he killed the troll, but the police so far only suspect. So what can he do to save himself? The only thing that he thinks links him to the murder is this fingerprint.

In reality, the print might be from his left hand rather than his right. The print might not even be his, but some other random friend that happened to visit the day before.

But because of his fragile state of mind, he reasons that the print is his, and the probability is that it's from his right hand. So he (almost) gets rid of the only evidence linking him to the murder, in his own mind.

Besides, I'm guessing he wouldn't want to lose both hands on the off chance it's a fingerprint from his left hand. I'm sure he'd rather have a hand left (pardon the pun).


The print was on the sim card- if he's right handed it makes sense that he would take the sim card out of the phone with his dominant hand- thus he only had to destroy his right fingers.

  • Hi @user46725, Have you done any research to back this up? ELU prefers answers which show some amount of research effort. If possible, include this info in your response. Thanks!
    – freeling10
    Commented Feb 10, 2017 at 4:51

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