not sure whom the, 'us', refers to in your case. But I will give it one try for you.
Early, in the worst shoot-out the FBI ever had, an Agent shot a Creep in the ribcage with a 9mm from a short distance. The bullet, while on the correct target path and with sufficient velocity, deformed and stopped before the bullet traveled thru to the Creep's vitals. Said Creep continued his attack despite soaking-up his new less than lethal gunshot wound to his chest.
The official FBI shooting review concluded that had 9mm been loaded with a bullet capable of decent penetration the Creep most likely would not have had the energy to kill, and injure, multiple Agents, shortly after the intial hit.
Reflecting on the tone from your request for this 25 year old open-source information, I am certain that others, whom may know more about the Dade County Shooting than me, will gladly fill in the details if you so desire.
That means absoutely nothing. A single bullet situation proves NOTHING. People have been hit with all kinds of great preforming bullets that did not live up to the expectations. The difference between a solid hardcast and a solid softer bullet is marginal.
As for your last comment, I know all about the shooting. I simply couldnt believe that anyone would translate that to a solid bullet at 18bhn(hardcast) would be any better than one at 8bhn. Hardcast vs softer lead isnt that kind of issue. Better load is the issue.
By your standard everyone carrying a 9mm better not carry HP ammo, there is a chance it would expand and not penetrate deep enough.