Were the other 37 really needed? The phrase "beating a dead horse" comes to mind.
It was a team effort:
- 23 stabbed Caesar.
- 23 carried a concealed dagger and passed it to a stabber.
- 10 were on the adjacent streets making sure nobody was coming.
- 4 convinced Caesar to go for a walk.
You left out the best part. After he was dead there were non-participants afraid of being called cowards. They put their hands in the blood then ran outside to show the public, braggig about the kill and saying, "this is Caesar's blood!" Later, when the political wind changed, they were tried and they claimed to have been present, but not armed. Witnesses from on the street asked why their hands had been red, and hey were executed. That's where we get the term, "caught red-handed." 
Trufax!