I recommend referring to the NCAA Softball Scoring Rules when looking for further guidance than the ASA Rule Book provides. Section 24 refers to the Earned Run, which are “runs for which the pitcher is statistically accountable” and are charged to the pitcher when a runner scores because of
1) a base on balls
2) a fielder’s choice
3) a hit
4) a batter hit by a pitch
5) an illegal pitch
6) a sacrifice bunt (including a slap and running slap)
7) a sacrifice fly
8) a stolen base
9) a wild pitch (including a third strike wild pitch)
All good information, though in my opinion the key sentences in the section is “Earned Runs are determined by reconstructing the inning as if there were no errors or passed balls. The pitcher should be given the benefit of the doubt in determining the advancement of the runners had the defense been errorless.” From these two statements, we have the basic guidelines we need to determine whether a run is earned or not.
I will take the example on which reader Ron provided clarification to me, and which led me to find the NCAA Softball Scoring Rules in the first place (he was quoting MLB scoring rules, and I needed to find the equivalent Softball scoring rules to confirm that what he told me applied to Softball. It did.). The first batter of the inning hits a base hit to center field, but the centerfielder misses the ball, and by the time she retrieves it, the batter circles the bases and scores. The hit is scored a single and the batter advanced on a three-base error. As it stands, this would be an unearned run. However, the next batter hits a home run over the fence. The third, fourth, and fifth batters of the inning are retired in order. The answer to the question “How many earned runs should be charged to the pitcher?” is two. If we reconstruct the inning assuming no errors were made, then the first batter would have been on first with her single, and then driven in by the home run.
The exception to this rule is if the pitcher starting the inning is replaced by a relief pitcher during the inning. Only the pitcher starting the inning gets the benefit of the “reconstruct the inning as if there were no errors made” rule. This means that the relief pitcher can be charged for earned runs that do not appear in the team totals. Let us use a new example to illustrate this. The first pitcher retires the first two batters in order for two outs, and then is relieved by a second pitcher. The next batter gets on via an error, and then scores when the next batter hits a triple. The fifth batter of the inning strikes out for the third out. The run is an unearned run for the team statistics, as the error would have been the third out. However, for the second pitcher, it is scored as an earned run because the run was driven in by a triple.
If the relief pitcher comes in during a batter’s plate appearance mid-count, which pitcher is responsible for the batter, the pitcher who started the plate appearance, or the pitcher who finished it? It depends on the count on the batter and whether the batter walks after the relief pitcher enters the game. Section 24d applies, and I will paraphrase it to simplify: if there are at least two balls on the batter and less strikes than balls on the batter, and the batter walks, we judge the first pitcher “more” responsible for the walk than the second pitcher, and charge the first pitcher with the batter. Otherwise, the batter gets charged to the second pitcher, even if she strikes out.
Finally, ASA and NCAA have the same rule when it comes to the runner who starts on second base because the tiebreaker is in effect and she scores. That is an earned run, but is not charged to the pitcher’s individual statistics.