Question: Through the course of the seven books, we learn more about Snape’s life. We learn that he was a Death Eater, and that he was in love with Harry’s mother, Lily.

Before James and Lily's death, he came to Dumbledore to beg him to protect them.

Dumbledore wanted something from Snape in return.

Was Dumbledore asking to *spy* on the Death Eaters (meaning he was already a Death Eater)? Or was he asking Snape to *become* a Death Eater?

Answer: 
Severus Snape was already a Death Eater.

He approached Dumbledore after having already told Voldemort about the prophecy.

> 
> “What request could a Death Eater make of me?”
> 
> 
> “The — the prophecy . . . the prediction . . . Trelawney . . .”
> 
> 
> “Ah, yes,” said Dumbledore. “How much did you relay to Lord Voldemort?”
> 
> 
> “Everything — everything I heard!” said Snape. “That is why —
>  it is for that reason — he thinks it means Lily Evans!” 
> 
> 
> “The prophecy did not refer to a woman,” said Dumbledore. “It
>  spoke of a boy born at the end of July —” 
> 
> 
> “You know what I mean! He thinks it means her son, he is going to
>  hunt her down — kill them all —”
> 
> 
> “If she means so much to you,” said Dumbledore, “surely Lord 
>  Voldemort will spare her? Could you not ask for mercy for the mother,
>  in exchange for the son?”
> 
> 
> “I have — I have asked him —”
> 
> 
> “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?”
> 
> 
> “Hide them all, then,” he croaked. “Keep her — them — safe. 
>  Please.” 
> 
> 
> “And what will you give me in return, Severus?”
> 
> 
> “In — in return?” Snape gaped at Dumbledore, and Harry expected
>  him to protest, but after a long moment he said, “Anything.”
> 
> 
> 

Early we see Lily say,

> 
> You and your precious little Death Eater friends — you see, you don’t even deny it! You don’t even deny that’s what you’re all aiming to be! You can’t wait to join You-Know-Who, can you?
> 
> 
>
**Snape was already a Death Eater.**

He was well-placed in Voldemort’s ranks. While acting as a Death Eater, he overheard Trelawney’s prophecy. He relayed this to Voldemort, who interpreted it to mean Harry, and by extension, Lily. It was only when Snape realised Lily was in danger that he sought Dumbledore’s protection, and turned himself in.

Indeed, when he comes to see Dumbledore, he is called out as a Death Eater:

> 
> Dumbledore flicked his wand. Though leaves and branches still flew through the night air around them, silence fell on the spot where he and Snape faced each other.
> 
> 
> “What request could a Death Eater make of me?”
> 
> 
> — *Deathly Hallows*, chapter 33 (*The Prince’s Tale*)
> 
> 
> 

And per Dumbledore’s testimony at Karkaroff’s trial:

> 
> “I have given evidence already on this matter,” he said calmly. “Severus Snape was indeed a Death Eater. However, he rejoined our side before Lord Voldemort’s downfall and turned spy for us, at great personal risk. He is now no more a Death Eater than I am.”
> 
> 
> — *Goblet of Fire*, chapter 30 (*The Pensieve*)
> 
> 
>