Dumbledore considered Quirrell to be greedy, hateful and ambitious, a reason why Quirrell could not understand the powerful magic of love, which was what heavily injured him during the battle with Harry Potter.
Dumbledore always figured Voldemort would find a way back. And, one of hos best tools for that eventuality had always been Severus Snape, the double agent. If there was a concern Quirrel was helping Voldemort, then Snape openly outing him for cursing Harry would have been a poor move.
Dumbledore's lack of belief that Sirius is innocent is also suspect. Sirius was a member of the Order of the Phoenix which fought against Death Eaters, but Sirius also was as close to James as a brother, the Potters even took him in when he ran away from home.
Until after Harry returned from the graveyard after the third task, Dumbledore did not suspect Mad Eye Moody. It was only when in the heat of the moment that Crouch Jr. momentarily forgot his role and tool Harry out of Dumbledore's sight that Dumbledore put the pieces together.
Snape's explanation to the Death Eaters was that he knew nothing of Voldemort's involvement, but "saw only greedy and unworthy Quirrell attempting to steal the stone." It was confirmed in Deathly Hallows that Snape had been "keeping an eye" on Quirrell on Dumbledore's orders.
How Dumbledore Knew That Quirrell Was Voldemort - Harry Potter Theory
Was Dumbledore suspicious of Quirrell?
On Hallowe'en, he let a troll into the Dungeons of Hogwarts Castle. This was a diversion so he could reconnoitre the defences around the Stone. As Dumbledore was suspicious of Quirrell, he had tasked Severus Snape with keeping an eye on the latter.
With the return of his Death Eaters at the end of Book Four, Voldemort declared that Snape had left their ranks forever. Conversely, Dumbledore went on declaring his undying trust in Snape. So Dumbledore was no more wrong than was Voldemort.
He kept Moody alive under the Imperius Curse to continue harvesting hair for the Polyjuice Potion, and to question him about his personality, behaviour and knowledge, in order to make the act more convincing.
“You disgust me,” said Dumbledore, and Harry had never heard so much contempt in his voice. Snape seemed to shrink a little, “You do not care, then, about the deaths of her husband and child? They can die, as long as you have what you want?” Snape said nothing, but merely looked up at Dumbledore.
Why didn't Arthur Weasley know Sirius was innocent?
Its not until lupin discovered that Peter P (wormtail) was still alive that Sirius was innocent and he did not portray the potters or kill wormtail. Therefore Mr weasley thought all along Sirius had the potters killed and though he was out to kill harry because he was the last potter and also he was his grandfather.
Peter Pettigrew, the Secret Keeper for the Potter family who betrayed them to Voldemort. Sirius Black was originally meant to be the secret keeper for James and Lily Potter, but Sirius thought Voldemort was on to him (he thought that Remus Lupin was a spy), therefore passing on the Secret Keeper to Peter Pettigrew.
Professor Quirrell was a temporary type of Horcrux while Voldemort inhabited his body, which is confirmed in the Wizarding World. It is possible that Voldemort created more temporary Horcruxes, such as the animals he possessed while in ghostly form.
As it turned out, Quirrell was a servant of Voldemort, and it was he, not Snape, who was aiming to steal the Philosopher's Stone for the Dark Lord, and, if possible, kill Harry along the way.
This jinx was used by Quirinus Quirrell on Harry Potter's Nimbus 2000 in early November 1991, during a Quidditch match. It was an attempt to murder Harry for Lord Voldemort. No one in the stands detected Quirrell of using this jinx, except Professor Severus Snape, who attempted to save Harry with a counter-curse.
During the 1994–1995 school year, Barty Crouch Jnr (disguised as Alastor Moody) transformed student Draco Malfoy into a white ferret and bounced him up and down, as punishment for attempting to attack fellow student Harry Potter from behind, earning Draco the nickname of "The Amazing Bouncing Ferret".
When Barty Crouch Jr was disguised as Mad Eye Moody | Fandom. How did he disguise his voice? Because polyjuice potion doesn't actually change the voices. In the book, the voices also change.
In the film version, Barty Crouch Jr. has the habit of licking his lips when threatened, in a snake-like way, to which he occasionally shows while under the disguise of Alastor Moody. This action led to him giving himself away to his father following the second task of the Triwizard Tournament.
Harry describes Umbridge to Sirius Black, saying that she's vile enough to be a Death Eater, despite not being one. Umbridge is also depicted to be a prejudiced person, despising half-breeds and Muggle-born witches and wizards to the point of firing Hagrid due to his half-giant birth status.
Mundungus' betrayal caught Moody by surprise and gave Voldemort enough time to cast the Avada Kedavra and kill Mad-Eye Moody. After he was brutally killed by Lord Voldemort, Moody's dead body tragically fell from his broom.
Lucius Malfoy was one of the many Death Eaters who denied their allegiance to Voldemort after the end of the First Wizarding War and therefore would be a perfect example of the kind of person Barty Crouch Jr. hates the most.
Did Snape know Harry was under the invisibility cloak?
Dumbledore was doing James a favour by helping him pass down the Invisibility Cloak to his son Harry. Snape definitely knew because in book 4 when Harry sees crouch in Snapes office, he's in his invisibility cloak. As soon as snape sees the golden egg and the map he says 'potters here' to mad eye. Potters here.
Bellatrix Lestrange (née Black) is the first female Death Eater introduced in the books. Aunt of Draco Malfoy and Nymphadora Tonks. She was introduced in Harry Potter and the Order of the Phoenix. She is the most faithful member of Voldemort's inner circle.
