Although the first and last words of the poem are spoken by an unnamed, third-person narrator (like you'd find in a novel or a short story), most of the poem is spoken by Guenevere, the wife of the legendary King Arthur.
What kind of a speaker is Guenevere? Well, she talks a lot, but she doesn't really tell us much that we can use. Picture that you're part of the jury while she's on trial. Sure, she gives a LOT of vivid detail, incorporating all of the body's senses, but she doesn't offer many facts, does she? Did she or did she not have sex with Sir Launcelot? Is she guilty of the crime she's been accused of? She was found in some sketchy situations, and she admits that she smooched with Sir Launcelot in a garden, but is that all?
As you read through the poem, take note of the ways Guenevere avoids answering questions (and, in fact, raises more questions) rather than providing evidence that might get her off the hook.