He points out -- so does Harvey Silverglate whose seminal 2008 book "Three Felonies A Day" is cited -- that prosecutors often overcharge as a strategy to win cases (and induce defendants to take plea deals often requiring them to agree to a prosecutor's recommendation for a prison sentence of some sort) through what I will term a war of attrition.
However, Will totally ignores some major points. First, the problem with abusive prosecutorial over-zealotry is that it threatens to ruin its victims. A defendant who successfully argues his or her innocence likely does so at the cost of financial ruin, never mind emotional ruin.
Secondly, it seems that the zeal to prosecute is not the same as, and does not involve, the zeal to actually investigate. It would be good to see this investigative determination when it comes to complex financial and terrorism cases, wouldn't it?
Finally, no analysis of legal and prosecutorial behavior is complete without recognizing the much tighter legal labor market at all levels. The oversupply of lawyers from years and years of too many law schools with little to no distinction and equally undistinguished law graduates entering the legal job market 400 to 500 per year per school, each year, finally had its predictable consequence when the 2008-09 recession hit. Demand by paying clients for legal services has been flat by many accounts since then, leading to some amazing downward pressure on salaries from a gross oversupply of lawyers (although arguably, top legal talent is still hard to find - or harder to motivate) in the face of flat (at best) customer demand.
How does this impact overcriminalization? One result of this is that government lawyers -- and particularly prosecutors at all levels -- have to have become increasingly worried about their ability to get and keep private sector jobs. It is foreseeable that prosecutors would seek to become increasingly marketable, and to win the prosecutor-recruiting beauty contests by firms. In other words, prosecutorial decisions may have become increasingly driven not by justice, but by prosecutors' zeal to compete for private sector (i.e., defense lawyer) job openings.
In such a market, justice, never mind diligence in making charging decisions, is unlikely to get much consideration at all.