At the end of the Harry Potter and The Goblet of Fire, Dumbledore tells the school that it was Voldemort who killed Cedric Diggory. However, it was actually Wormtail (Pettigrew) who killed Diggory. So why did he say it was Voldemort? And none of the trio seemed to have any issues with Dumbledore telling that lie. Why didn't they care?
There's a few reasons for this so I will explain each one in turn.
Voldemort gave the order
When a leader gives the order to kill that kill is generally associated with them.
From far away, above his head, he heard a high, cold voice say, 'Kill the spare'
A swishing noise and a second voice, which screeched the words to the night: ’Avada Kedavra’
Harry Potter and the Goblet of Fire
It was done using Voldemort's wand
This would either mean people would assume Voldemort did it himself (assuming they could tell it was Voldemort's wand of course) or that it was highly likely Voldemort was involved/gave the order for the kill.
Rorujin: Did Wormtail used Voldemort's wand to kill Cedric? Is it why Cedric comes out of Voldemort's wand even though was Wormtail who killed him?
JK Rowling replies -> Correct!
Harry's came back muttering about Voldemort clutching the dead body
It's highly likely in a situation when a boy comes back clutching a dead body and muttering one name over and over again that you would assume the person belonging to that name did the kill.
"He's back," Harry whispered. "He's back. Voldemort."
"What's going on? What's happened?" The face of Cornelius Fudge appeared upside down over Harry; it looked white, appalled. "My God - Diggory!" it whispered. "Dumbledore - he's dead!"
Harry Potter and the Goblet of Fire
Pettigrew was presumed dead and a hero
It would be quite odd to say a hero came back from the dead only to kill an innocent student.
"There, now, Minerva," said Fudge kindly, "Pettigrew died a hero's death. Eyewitnesses -- Muggles, of course, we wiped their memories later -- told us how Pettigrew cornered Black. They say he was sobbing, 'Lily and James, Sirius! How could you?' And then he went for his wand. Well, of course, Black was quicker. Blew Pettigrew to smithereens..."
Harry Potter and the Prisoner of Azkaban
It isn't as complicated as all that. It is true that Dumbledore was lying (he knew the truth; by that point, Harry had told the entire story in detail) but nonetheless his statement was essentially true. Voldemort had in fact returned; and he was in fact responsible for Cedric's murder, since he gave the order. That's all that really mattered, and it was all that needed to be said. Pettigrew, by that point, was irrelevant.
Interestingly, this concept is recognized in real-world law; there's a recent article on Popehat that talks about defamation and the "substantial truth doctrine."
That's the notion that even if not every word of a statement is literally correct, if it is materially true — that is, if the important facts that determine how the audience views it are true — then it's true for purposes of defamation law, and not defamatory.
Dumbledore couldn't have told the entire truth just then; as Raditz points out in the comments, it was too incredible, too complicated, and he'd have completely lost his audience. Harry, Ron, and Hermione might not fully appreciate that, but they could certainly recognize that what Dumbledore said, if not strictly true, was not materially false. There was no reason for them to object to it.
In case anyone is curious as to why I'm sure Dumbledore already knew the details, this quote is from chapter 36:
'If I thought I could help you,' Dumbledore said gently, 'by putting you into an enchanted sleep, and allowing you to postpone the moment when you would have to think about what has happened tonight, I would do it. But I know better. Numbing the pain for a while will make it worse when you finally feel it. You have shown bravery beyond anything I could have expected of you. I ask you to demonstrate your courage one more time. I ask you to tell us what happened.'
The phoenix let out one soft, quavering note. It shivered in the air, and Harry felt as though a drop of hot liquid had slipped down his throat into his stomach, warming him, and strengthening him.
He took a deep breath, and began to tell them. As he spoke, visions of everything that had passed that night seemed to rise before his eyes.
Of course we later discover that Dumbledore, not to put too fine a point on it, is not exactly in the habit of telling anyone the entire truth. One might even consider Dumbledore's speech to be a subtle foreshadowing of the revelations in Deathly Hallows.
Mind you, Dumbledore is in good company:
So what I told you was true, from a certain point of view.
-- Obi-Wan Kenobi, Return of the Jedi
Out of universe, however, I suspect that this was simply a continuity error.
If the intent was for Voldemort to have killed Cedric personally that would explain a number of things: not only Dumbledore's speech, but also why the Priori Incantatem created an echo of Cedric. The official explanation for the latter event is that Wormtongue was using Voldemort's wand, but that seems unlikely, and if that were the original intent I would have expected it to be reflected in the text.
Dumbledore assumed it was Voldemort
My answer is based on the books. So here it is.
In Chapter 35: Veritaserum, Harry returns with Cedric's body back at the entrance of the maze after narrowly escaping his own death by the hands of Lord Voldemort. And the first thing he says is-
"He's back," Harry whispered. "He's back. Voldemort."
"What's going on? What's happened?" The face of Cornelius Fudge appeared upside down over Harry; it looked white, appalled.
"My God - Diggory!" it whispered. "Dumbledore - he's dead!" The words were repeated, the shadowy figures pressing in on them gasped it to those around them . . . and then others shouted it
screeched it -
into the night -
"He's dead!" "He's dead!" "Cedric Diggory! Dead!"
"Harry, let go of him," he heard Fudge's voice say, and he felt fingers trying to pry him from Cedric's limp body, but Harry wouldn't let him go. Then Dumbledore's face, which was still blurred and misted, came closer.
"Harry, you can't help him now. It's over. Let go."
"He wanted me to bring him back," Harry muttered - it seemed important to explain this. "He wanted me to bring him back to his parents...."
"That's right. Harry.. just let go now."
Dumbledore bent down, and with extraordinary strength for a man so old and thin, raised Harry from the ground and set -him on his feet. Harry swayed. His head was pounding. His injured leg would no longer support his weight. The crowd around them jostled, fighting to get closer, pressing darkly in on him - "What's happened?" "What's wrong with him?" "Diggorys dead!"
HP: Goblet of Fire Chapter 35 Veritaserum
At this point, Harry never told anyone that Cedric Diggory was murdered by Wormtail; his only indication was that He-Who-Must-Not-Be-Named is back and Diggory is dead.
Later when the fake Mad-Eye (Crouch Jr.) is caught and everything settles, Harry and Dumbledore have a talk and Harry explains how he was able to see the ghosts of his parents and Cedric:
But when he reached the part where the golden beam of light had connected his and Voldemort's wands, he found his throat obstructed. He tried to keep talking, but the memories of what had come out of Voldemort's wand were flooding into his mind. He could see Cedric emerging, see the old man, Bertha Jorkins... his father... his mother...
He was glad when Sirius broke the silence.
"The wands connected?" he said, looking from Harry to Dumbledore. "Why?"
Harry looked up at Dumbledore again, on whose face there was an arrested look.
"Priori Incantatem," he muttered.
HP: Goblet of Fire Chapter 36 Parting of the ways
From what Dumbledore heard and knew at this point of time was that:
- Diggory was dead and Voldemort is back
- Diggory's ghost appeared when Harry's wand connected with Voldemort's indicating that Voldemort's wand was used to kill Cedric.
Dumbledore made a logical assumption (but far from what actually happened) that it was Voldemort who killed Diggory. And he made his announcement about Cedric's murder by Voldemort's hands at the Main Hall.
PS: Additionally, neither Ron nor Hermione had any idea (at least at the time when Dumbledore made the speech) that Wormtail was the one who killed Cedric Diggory.
But for Riddle's actions, Diggory would not have died
Murder was not Wormtail's style or habit. Death eater or not, he's not the sort to go murdering school kids for no reason. If Riddle had said "make the spare go away", Pettigrew would have as likely told him to touch the goblet again, or apparated him to Timbuktu.
Pettigrew didn't have much of a choice, and had no viable path by which he could have saved Diggory if he wanted to. If he had refused, it is 100% foreseeable that Riddle would have instantly and gleefully killed Pettigrew and then killed Diggory all the same. If Pettigrew apparated away with Diggory, they would be wrathfully hunted, same end.
Riddle killed people all the time, and all of his followers knew that when he said kill, that wasn't a joke. There wasn't any ambiguity.
So in the measure of things, gauging who is most responsible, the bulk of the weight of the murder rests on Riddle. But for his command...
Dumbledore's statement, thus, is the most legally correct way to say it.
Mind you, nothing about murder says only one person can be charged for the murder. Everyone who meets the legal definition is guilty.
Well it is true that Voldemort had him killed. Wrong place wrong time. Unfortunately Cedric Diggory was in that precise predicament. It was by his order by his people so it’s like doing it Himself. He also choose Wormtail who cannot disobey because he had no way out of doing it without being fed to Nagini. Because of the fear and knowing that it was either his life or Cedric’s he did it out of fear not to please the Dark Lord like other death eaters would gladly do. The blame of taking Cedric’s last breath is Pettigrews but Voldemort hold most of the blame for ordering the man that is scared of death and him to kill a innocent bystander. Dumbledore has stated before that murder is murder One person must be charged for it. Everyone that has a part in it is guilty so in the end the blame can be put on both but Dumbledore chooses one; the most threatening one who has a history of killing numerous people and ordering people to do so in his name