In Chapter Nineteen of Prisoner of Azkaban after a lengthy discussion in the Shrieking Shack, Lupin and Sirius decide to kill Pettigrew:

"You should have realized," said Lupin quietly, "if Voldemort didn't kill you, we would. Good-bye Peter."

In the end Harry prevents them from doing it, but why would they have done it in the first place? In order to clear Sirius they would have to present Pettigrew, either alive or dead, as mentioned in Chapter Twenty-One:

"Sirius has not acted like an innocent man. The attack on the Fat Lady – entering Gryffindor Tower with a knife – without Pettigrew, alive or dead, we have no chance of overturning Sirius's sentence."

However, if they turn up with Pettigrew dead then they have to explain how he died. It would then be possible, even probable, that the Ministry would realize that they were the murderers. Murdering a fellow human being carries a life sentence in Azkaban, as per Chapter Fourteen ofGoblet of Fire:

"Now... those three curses – Avada Kedavra, Imperius, and Cruciatus – are known as the Unforgivable Curses. The use of any one of them on a fellow human being is enough to earn a life sentence in Azkaban.

Why would Lupin risk a life sentence in Azkaban just to kill Pettigrew? And from the context it does not appear that this was a rash decision in a fit of passion. He seems to have calmly decided that this is the best course of action, without any concern for the consequences.

  • 11
    It's all very well to second-guess them, but it's not like keeping him alive worked out all that well for them either! May 28, 2019 at 1:08
  • 8
    Per your last quote, technically it is using Avada Kedavra to kill someone that carries a life sentence; I suppose it is possible that murder by more mundane means may carry a lesser sentence, particularly if there are mitigating circumstances.
    – Beofett
    May 28, 2019 at 18:30
  • 1
    1. "... alive or dead, we have no chance of overturning Sirius's sentence" Presumably they had the idea that a dead Pettigrew will still be enough to overturn the sentence. 2. "...The use of any one of them on a fellow human being is enough to earn a life sentence in Azkaban." It's avada kedavra (or any one of the 3) that carries a life sentence, not necessarily just killing someone
    – user13267
    May 29, 2019 at 10:51

5 Answers 5


If they killed Peter Pettigrew, they could simply claim that he died in the course of his capture. They don't need him to be alive to prove that Sirius was innocent; they just need his body.

Pettigrew was a Death Eater, who had successfully pinned one of his previous crimes on someone else, and who had managed to evade detection and capture for over a decade. He's clearly a dangerous and ruthless individual who is capable of taking extreme acts to remain free (like pretending to be a pet rat for years at a time). No one would blink an eye if you failed to bring him in alive.

Of course, telling that lie would require Lupin and Black to be less than perfectly honorable and scrupulous, but they weren't saints.

  • 39
    So...Harry was arrested when he killed Voldemort? All three times? And when he killed Professor Quirrell? There seems to be pretty broad latitude for self-defense in the wizarding world. And necessarily so - just about everyone is armed at all times. And even people who aren't armed - including elementary school age children - are dangerous.
    – tbrookside
    May 27, 2019 at 23:36
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    Harry never used Avada Kedavra... It was by (I feel uncomfortable saying this) chance that Harry killed those people. Voldemort only died because his own curse rebounded!
    – user112267
    May 27, 2019 at 23:37
  • 25
    They don't need to use Avada Kedavra to kill him. Lupin never even begins his spell before Harry springs to Pettigrew's defense, so we don't have a way of knowing what spell he was going to use. Heck, Levicorpus can be fatal if you use it correctly. (Maybe not inside a cramped cabin room, but still.) There must be dozens of spells that can be used to kill.
    – tbrookside
    May 27, 2019 at 23:42
  • 4
    @INTERESTING I mean one of the early spells they learn (Wingardium Leviosa) is easy enough to kill with. Levitate a person high enough (~100 feet) and drop them, they'll likely die. Levitate an object and drop it on them (such as a troll's club or a piano), they'll also likely die. There's so many options for them to kill Pettigrew with without resorting to the Unforgivables, and even without resorting to anything approaching a "dark" curse. May 28, 2019 at 17:46
  • 24
    @Joshua Yeah, Rowling definitely didn't playtest her low-level spells for balance. The mage class is definitely broken.
    – tbrookside
    May 28, 2019 at 18:59

He wanted revenge...

...for Jame's and Lily's deaths. After all, it was Pettigrew that caused them to die!

“Harry, this piece of vermin is the reason you have no parents,” Black snarled. “This cringing bit of filth would have seen you die too, without turning a hair. You heard him. His own stinking skin meant more to him than your whole family.”

As for the Ministry realizing that they were murders, everybody thinks Pettigrew is dead, anyway! They would never realize that he had actually been murdered!

“When I cornered him, he yelled for the whole street to hear that I’d betrayed Lily and James. Then, before I could curse him, he blew apart the street with the wand behind his back, killed everyone within twenty feet of himself — and sped down into the sewer with the other rats...”

After they've killed him, it's easy to lie about how he died. Perhaps the all-consuming guilt forced Peter to put a wand to his head and say Avada Kedavra! After being confronted by Lupin and Sirius, he began to finally feel remorse for his actions.

(There are possibly better lies out there! I'm not great at lying, myself!)

So, really, they have nothing to lose by killing him, they would get their revenge, and nobody would find out! Brilliant!

  • 3
    They need to produce the body in order to clear Sirius. Plus at that point Snape knew that Lupin was colluding with Sirius. And they would have to rely on Harry, Hermione, and Ron to keep quiet.
    – Alex
    May 27, 2019 at 22:53
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    @Alex "The risk would’ve been what made it fun..."
    – user112267
    May 27, 2019 at 22:58
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    "...without Pettigrew, alive or dead, we have no chance of overturning Sirius's sentence." This line makes it clear that it wasn't their goal to get rid of the body and pretend it didn't happen.
    – Laurel
    May 27, 2019 at 23:26
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    @JanusBahsJacquet knock him out with a stunner, cast a couple of shields and then use a cutting curse to end him, and the wand history will support their story rather than undermine it: a miss, a quick duel, and an unfortunately lethal cutter which was intended to disable his arm but ended up knicking his neck instead when he ducked unexpectedly.
    – Morgen
    May 29, 2019 at 1:45
  • 1
    @Morgen :D This made my day!
    – user112267
    May 29, 2019 at 2:07

This will not be strictly illegal

  1. Peter Pettigrew is a death eater. Aurors and other members have killed death eaters in the series. It is mentioned that Barty Crouch authorized to kill many death eaters during the rise of Voldemort. Mrs.Weasly was not arrested for killing Bellatrix.
  2. They don't have to use the unforgivable curses. Harry nearly killed Malfoy without using one. Sirius and Lupin are skilled wizards who can kill a person without using an unforgivable curse.

Besides, they could claim that it was an act of self-defence or they did it to defend Harry.

  • The laws on vigilantism must then be very lax in that universe. There is one thing to kill an enemy combatant in a war (like the death eaters during the rise of Voldemort) or killing in selfe-defense (like killing Bellatrix), versus summary execution during what was basically a "citizen's arrest".
    – vsz
    May 29, 2019 at 6:12
  • @vsz No one outside will know how it happened. They could claim it was a combat or self-defence or in defence of Harry.
    – Kolappan N
    May 29, 2019 at 6:16
  • You claimed this will not be illegal. Being illegal or not doesn't mean being found out or not.
    – vsz
    May 29, 2019 at 6:18
  • @vsz That depends on the Ministry. For example, Barty Crouch prefered to kill rather than capture but Mad-eye Moody always captured them alive if possible.
    – Kolappan N
    May 29, 2019 at 6:20

Lupin and Sirius were after justice and revenge. Neither of them had anything to lose and even if they had, they couldn't see past their hatred for Peter's betrayal of their best friend, to consider their own lives and the outcome.

Lupin, was a werewolf and his kind were not treated well by the Wizarding community. Most of them couldn't get jobs, and lived underground. He finally had friends at Hogwarts, best friends that meant so much to him, as well as how much Lily meant to him, and lost everyone.

"For the first time ever, I had friends, three great friends... I was terrified they would desert me the moment they found out what I was. But of course, they, like you, Hermione, worked out the truth... and they didn't desert me at all. Instead, they did something for me that would make my transformations not only bearable, but the best times of my life. They became Animagi.">

"Your mother was there for me at a time when no one else was."

Lupin goes to great lengths to emphasize how important his friends were to him. This makes the betrayal of one of his friends (Peter), and the recent realization that this whole time, one of his friends never betrayed James (Sirius) so much more powerful. He would not abandon him or try to stop Sirius after finding out the truth. He also wants justice for the betrayal.

‘You should have realised,’ said Lupin quietly. ‘If Voldemort didn’t kill you, we would. Goodbye, Peter.’


I think it was Sirius who wanted to kill him first.

“They’ve — got — a — right — to — know — everything!” Lupin panted, still trying to restrain Black. “Ron’s kept him as a pet! There are parts of it even I don’t understand, and Harry — you owe Harry the truth, Sirius!” Black stopped struggling, though his hollowed eyes were still fixed on Scabbers, who was clamped tightly under Ron’s bitten, scratched, and bleeding hands. “All right, then,” Black said, without taking his eyes off the rat. “Tell them whatever you like. But make it quick, Remus. I want to commit the murder I was imprisoned for…”

And Remus was the type of person who followed his friends plans, he was like that since he was a student. He didn't stop James and Sirius when they attacked Snape although he was a prefect! And he came along with them while breaking the rules. Creating the marauders map, accompanying them when they became unregistered animagus, and we don't know what else.

“I sometimes felt guilty about betraying Dumbledore’s trust, of course… he had admitted me to Hogwarts when no other headmaster would have done so, and he had no idea I was breaking the rules he had set down for my own and others’ safety. He never knew I had led three fellow students into becoming Animagi illegally. But I always managed to forget my guilty feelings every time we sat down to plan our next month’s adventure. And I haven’t changed…”

Perhaps he kinda felt like he always owed them, because no one else would have stayed his friend after learning his secret, let alone what they've done to make him feel better. Also he may have felt guilt because he was the reason Pettigrew became close to Potters and knew their place.

Remus, always the underdog’s friend, was kind to short and rather slow Peter Pettigrew, a fellow Gryffindor, whom James and Sirius might not have thought worthy of their attention without Remus’s persuasion. Soon, these four became inseparable.

-- Pottermore


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