The 1989 FBI paper entitled "Handgun Wounding Factors & Effectiveness" states page 11: The single most critical factor remains penetration. While penetration up to 18 inches is preferable, a handgun bullet MUST reliably penetrate 12 inches of soft body tissue at a minimum, regardless of whether it expands or not. If the bullet does not reliably penetrate to these depths, it is not an effective bullet for law enforcement use. FN36 Footnote 36 is: Wound Ballistic Workshop: "9mm vs. .45 Auto", FBI Academy, Quantico, VA, September 1987. Conclusion of the Workshop. So I went and found the 1987 Workshop. Guess what? The workshop concluded something different. Near the end it says: The single most critical factor remains penetration. A handgun bullet MUST reliably penetrate 10-12 inches of soft body tissue at a minimum, regardless of whether it expands or not. Penetration up to 18 inches would be even better. If the bullet does not reliably penetrate to these depths, it is not an effective bullet for law enforcement use. I wonder how 10-12 inches in 1987 became 12 inches in 1989? Perhaps they wanted to hold the ammo manufacturers to a higher standard? Perhaps they worried if they said 10-12 inches, they knew it would be interpreted as 10 inches? In any event, in the past I have looked at the 12" penetration standard as a pass fail test for my ammo selection. I don't think I am alone in that thinking. This discovery introduces shades of gray in the penetration standard. And if 10-12 inches of penetration is minimally acceptable for law enforcement (per the 1987 FBI workshop), this can have enormous implications for certain ammo.