So I've been re-reading Goblet of Fire and after reading Barty Crouch Jr's recounting of how he and his mother switched places in Azkaban via Polyjuice Potion, I'm unclear why Mrs. Crouch died while she was still taking Polyjuice.

If Mrs. Crouch's body was terminally ill, each time she took the Polyjuice wouldn't she have had Barty Crouch Jr's body, which was not terminally ill? Why, then, did she die very soon after Barty Crouch Jr was smuggled out of Azkaban? Shouldn't she have had her son's strength and health from the Polyjuice? Yes, Barty Crouch Jr was weakened by Azkaban, but he wasn't dying.

Deathly Hallows shows that the physical limitations or disabilities of the person providing the hairs for the Polyjuice Potion are transferred to the person taking the potion:

‘Harry, your eyesight really is awful,’ said Hermione, as she put on glasses.

Deathly Hallows -- page 49 -- Bloomsbury -- chapter 4, The Seven Potters

It would seem the same would go for healthy characteristics. As long as Mrs Crouch had a supply of Polyjuice Potion, shouldn't she have remained alive? It could be said that she ran out of Polyjuice and then died, but Barty Crouch Jr says implicitly that his mother died with Barty Jr's appearance, meaning the Polyjuice was still in her system and working at the time of her death.

Why did Mrs. Crouch die while taking Polyjuice Potion?

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    Pure speculation: Polyjuice potion only reproduces genetic disabilities, and Mrs. Crouch had a regular non-genetic disease.
    – jwodder
    Commented Sep 9, 2012 at 22:11
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    @ssg The book was first published in 2000, the movie was released in 2005. If you haven't read them by now then that's on you, you can't reasonably expect other people to consider plot lines from 12 years ago to be spoilers. Commented Sep 10, 2012 at 10:56
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    @AnthonyGrist I wasn't even browsing this web site. Don't you think it's still bad etiquette to slap spoilers on people's face on a global feed? Am I supposed to leave that to someone's discretion based upon their own understanding of when a commodity should be purchased? Commented Sep 10, 2012 at 11:33
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    @ssg -- It sounds like using the feed might not be the best course if you want to avoid spoilers. As Anthony Grist noted, the novel is 12 years old. I encourage you to read the series, though -- they're very enjoyable books. Commented Sep 11, 2012 at 4:02
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    If you don't like spoilers, the Internet is not a good place for you, honestly. Commented Sep 11, 2012 at 4:29

6 Answers 6


I believe it has everything to do with the limitations of the Polyjuice potion. Since we don't know what she died of, disease seems the most likely to me. And by looking at the effects of polyjuice potion, if my theory is right, it would explain why it didn't keep her alive.

Polyjuice potion alters the appearance of a person, meaning altering physical external characteristics to match that of the person being copied. It's clear that the polyjuice potion does not alter everything about the drinker. Some things must remain unchanged. For example, it must leave the brain alone, or the user would lose his or her personality.

Poor eyesight generally has to do with the shape of the cornea, or damage to it - an outward physical trait that would be copied exactly the same as the shape of the lips or leg. Hermione's eyesight was affected simply due to outward physical changes. It had nothing to do with sickness or disease.

Polyjuice potion appears to affect the shape of the body - at many levels, and various body parts, and also the color of the skin, hair, etc to effect the transformation. Diseased flesh, transformed to a different shape and/or color is still diseased.

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    There are some internal changes as well. In the books (not in the movies), Harry and Ron's voices change to the deeper voices of Crabbe and Goyle. This means at the very least that some internal structure changed (i.e. Voice Boxes etc).
    – NominSim
    Commented Sep 9, 2012 at 23:37
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    @NominSim - No argument there. My statement and point was only that it doesn't alter everything. Voice is at least partially related to the shape of the vocal cords, voicebox, mouth, etc. so even that is consistent with what I'm driving at. Polyjuice potion would alter some or all o those things as well. bigquestion.wordpress.com/2008/03/11/… I'm getting at the idea that polyjuice potion affects the shape of the body - at many levels to effect the transformation. Diseased flesh, transformed to a different shape is still diseased. Commented Sep 10, 2012 at 0:01
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    I agree with you're answer, just wanted to clarify that it wasn't only external characteristics that are copied. I definitely agree that it doesn't seem to alter everything.
    – NominSim
    Commented Sep 10, 2012 at 0:09
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    @Slytherincess - You're right of course. I changed the first part of the answer, keeping the rest of the answer the same. Commented Sep 11, 2012 at 3:25
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    Although you gave me a new thought to ponder... I wonder where the limit is. If you kept all the hair from your haircuts while youthful, could you achieve immortality and eternal youth by transforming into a younger version of yourself? Could Voldemort retained his youthful good looks by using Polyjuice potion instead of Horcruxes? Hmmmm. Commented Sep 11, 2012 at 3:31

We are never told what terminal illness that she has, but your assessment that physical characteristics seem to be transferred with the Polyjuice Potion is spot on. What we know that isn't transferred with the Polyjuice potion is the person's mind.

Therefore it seems most likely that the terminal illness with which Mrs. Crouch was dealing with, was a mental illness. In canon we see numerous techniques that wizards can use to heal physical maladies, yet the only (IIRC) mental malady that we know of; Neville Longbottom's parents, is apparently not treatable. Indeed there are several patients in the mental wing of the hospital. Perhaps in the wizarding world the treatment of mental illnesses is not something that magic provides much help with.

There is also this quote from the relevant passage in The Goblet of Fire:

They sensed one healthy, one dying person entering Azkaban. They sensed one healthy, one dying person leaving it.

So Barty Crouch Jr. was already dying inside Azkaban, so even if the Polyjuice potion gave her his health, he was already dying at that point (so much so that the Dementors did not notice his health compared to his mothers).

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    See, I read that as the Dementors sensed Mrs Crouch as the sick one coming in. Then Barty Jr and Mrs Crouch took the Polyjuice and Barty Crouch Sr left Mrs Crouch (Polyjuiced as Barty Jr, who was not dying) and left Azkaban with Barty Jr (Polyjuiced as Mrs Crouch, who was dying). If Barty Jr had been dying, there would have been no reason for the Polyjuice, because the Dementors are blind and wouldn't have been able to tell Barty Jr from Mrs Crouch. Does this mean the Polyjuice was done merely for the benefit of fooling the other Azkaban prisoners? I'm not so sure. Commented Sep 10, 2012 at 1:01
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    There is also the fact that Polyjuice potion is never mentioned as having those types of "healing" effects in canon. There are several times where it seemingly would have come up if that was the case. You would have expected Snape(being a Potions expert) to suggest it to Dumbledore at the least as a stop gap to his cursed hand.
    – NominSim
    Commented Sep 10, 2012 at 4:08
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    Of course this breaks down in reality since mental illnesses are (of course) physical. And very few kill you. Commented Sep 10, 2012 at 14:38
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    What @KonradRudolph said: I don't know of any fatal mental illnesses (not counting suicide resulting from, e.g., depression), and all illnesses, including mental ones, have a physical cause.
    – Martha
    Commented Sep 10, 2012 at 16:48
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    @KonradRudolph I made the distinction in the answer to point out that the mind is preserved during the transformation. So any mental defects in the person will remain. Also "very few kill you" is misleading, a lot of the most serious mental illnesses directly lead to death, even if the mental illness itself isn't the direct cause, it is the root of the problem in many cases.
    – NominSim
    Commented Sep 11, 2012 at 0:47

She possibly died from the same disease as someone from a totally different canon - Padme Amidala. From a broken heart, aka. loss of will to live.

She was already on the way there at Barty Jr.'s trial as seen in Dumbledore's Pensieve memories:

There was total silence, broken only by the dry sobs of a frail, wispy-looking witch in the seat next to Mr. Crouch. She was clutching a handkerchief to her mouth with trembling hands.


The wispy witch beside him gave a great gasp and slumped in her seat. She had fainted. Crouch appeared not to have noticed.


Here's my take. The intention behind polyjuice is to give the appearance you are someone else.

However, copying a fatal disease would be a bad idea. Losing your brain/memories would also be bad. Given polyjuice has been created by someone, and is well known/well used, it must have been well thought out and tested.

I think polyjuice would change what is necessary for the change to be authentic, without endangering you/your sanity.

If your face needs to change, it will. If your voicebox needs to change, it will. If you need to stumble around blindly without glasses, you will (nice one David Stratton, great example).

If the person you're copying is ill or mad, it's far safer to just act like you have that particular fatal disease, or that you're mentally ill. This would result in a very useful potion, instead of a possibly deadly potion.

With this in mind, I definitely took the 'one healthy/one dying' to mean his mum was dying, and he wasn't, and the polyjuice was for people who could see him. It makes more sense. If everyone thinks he's died inside, great. If his mum is terminal, why not pull this off? She's dying anyway.

The alternative is far less believable; his non-terminal mum swaps with him then dies. He's terminal then escapes and recovers.

As for his need to recover, I don't think it's related to dying. Azkaban is regarded as a pretty terrible place. It's entirely believable you'd need to recover after leaving. I think I would.

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    +1: you've said everything I was gonna say. Key parts: 1. Polyjuice is a disguise; it copies whatever parts are needed for the disguise. 2. The nursing back to health part was for the aftereffects of being in Azkaban.
    – Martha
    Commented Sep 10, 2012 at 16:44
  • Hey, whoever voted me down, what was that for? Let me know, I'm new at this...
    – Chris
    Commented Sep 12, 2012 at 11:14
  • +1 from me for the excellent reasoning behind your answer. I am thinking he either had a terminal illness and died after several months after he escaped, or he could get medical care after leaving because such care would be denied to a prisoner. (e.g. - If a prisoner is dying of pancreatic cancer, the prison won't pay for his surgery. Or if a prisoner needs a kidney transplant to live, the prison will say other patients deserve it more.)
    – RichS
    Commented Apr 21, 2018 at 7:33

I think the questioner, in this case, is thinking a little too much about the minute, undiscussed details of magic. I actually doubt that even J.K. Rowling thought of this herself. The problem with questions like this is that they tend to be answered with superfluous real-world knowledge of science or some other field. Everything Slytherincess says about the transfer of health-status accompanying the shape-shifting powers of Polyjuice Potion is very well thought out, with a lot of real-world logic applied to it - but that is just the problem, unfortunately: it's real-world logic applied to the illogic of magic. All we know about the Polyjuice Potion is that it is designed to make one human look (and sound) exactly like another; how and why the disease of Mrs Crouch wouldn't have been cured by Barty Crouch Jr's essence in the Polyjuice Potion is unanswerable. I'm afraid we don't know. To provide any other sort of explanation is just speculation. However, since Mrs Crouch did still have her disease whilst in her son's form, we have proof that drinking Polyjuice Potion with the hairs of a healthy person in it will not cure someone of a disease; within J.K. Rowling's world, anyway.

  • I think you make excellent points and, yes, sometimes I do overthink Potterverse. In my defence, I will say that it's not intentional -- I never purposefully look for questions to ask that I know are unanswerable. I do have a lot of questions in my mind that are not answerable and I recognize that, so I just keep them there, tucked away. Not only is asking unaswerable questions unfair to my fellow SFF.se users, it's not really enjoyable as the person asking the question to not get any answers. Thank you for reminding me to keep things in perspective. :) +1 Commented Apr 3, 2014 at 18:38

Polyjuice is a disguise and just that; it would not reporduce/cure illness, simply give the outward appearance of them as much as required; she still died, despite being in Barty's form. Along with the mind, there are obvious limitations to the change.

Barty appeared to be dying to the Dementors, because that was part of the apperance the Polyjuice was required to create. The 'nursing back to health' would be from Azkaban's after affects; if he was truly dying, then he wouldn't have been able to recover, and would have made his mother's trade pointless.

Alternativly, they both could have had illness (retained in the change) and the Dementors couldn't tell the difference/couldn't be bothered; Mrs. Crouch's decline since the trial, and Barty's Dementor-fed-upon mind. His was environmental, so once clear of it, he could recover, but she would get worse, and succumb.

The dementors didn't check the disguised Mrs. Crouch. They made sure the same 'feeling' people came and left; anyone sneaking in would be illogical to them. They could have sensed her misery, but they wouldn't have considered that amiss in Azkaban.

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