He walked out accompanied by the signature tap of his walking cane on concrete — a shrapnel wound that had never healed.
-- Narrator (Chapter 1)

Importance: When Allie and Joseph located Jake after he faked his death, they discovered that he was not using a cane. The cane was apparently a prop he used to get sympathy. Rosco found Jake’s cane close to the wreck site. Joseph thought at the time that it was strange that the cane was not damaged.

He was found unresponsive, zip-tied, and lying in the back of a patrol vehicle with several weapons and a backpack full of both drugs and cash.
-- Narrator (Chapter 7)

Importance: Joseph tracked Juan down, killed him, and left him where police officers could find his body. Even though Joseph clearly reverted to violence to kill Juan, Catalina praises him for being a good man.

If I were you, I’m not sure I’d trust me either...
-- Joseph (Chapter 8)