A phrase that liars use as a last ditch attempt to instill belief in themselves to the person they're trying to con. It's always easy to spot a bullshitter when they pull out the infamous "I swear to god!"
Cop: "Are these your needles and crack pipes that I found in your car and jacket pockets?"
Burn out highschool kid: "No they're not! I swear to god they're not! I SWEAR TO GOD!"