The NFL has spoken and Kansas City Chiefs DE Shaun Smith is guilty.
Per Jay Glazer of FOXSports.com, the NFL has fined Smith $10,000 for grabbing 49ers RT Anthony Davis below the belt.
There is video evidence of the incident (above).
Davis was slapped with a personal foul penalty on the play for hitting Smith after the incident.
In Week 2, Smith was accused by Cleveland Browns C Alex Mack of grabbing below the belt. Smith was not penalized or fined in Week 2. In Week 3, Davis confirmed after the game that Smith had grabbed him below the belt.
On the TV broadcast of the Week 3 game against the San Francisco 49ers, you can see Todd Haley saying what appears to be something along the lines of "tone it down" to Smith after Davis was penalized.
Chiefs head coach Todd Haley said this week that the officials are very good at their job so he goes by what they say.
So that's that.