"I should of knew," George said hopelessly. "I guess maybe way back in my head I did."
Chapter 5 · George Milton
Context
George has just examined the body and confirmed Curley's wife is dead. He responds to Candy's question about what has happened by acknowledging that on some level he had anticipated this outcome.
Analysis
The locution 'way back in my head' constructs the mind as a spatial location with a hidden interior—knowledge that exists without having been accessed, anticipation without conscious anticipation. The repetition of 'I should of knew...I did' moves from counterfactual obligation ('should of') to flat indicative confession ('I did'), tracking George's confrontation with his own complicity in the dream he sustained despite knowing its impossibility. 'Hopelessly' is the adverbial signature of belated knowledge.
How to Use in Essay
Support a thesis that George's tragedy is one of knowing without acknowledging—he has, throughout the novella, performed for Lennie a hope he himself did not hold, and this moment marks the collapse of that necessary fiction.