How many hundreds (or thousands?) of ACCA prisoners could be impacted by a big ruling in Johnson?

The Supreme Court Term is winding down, and we might get a ruling as early as this coming wee in the (re)argued case Johnson v. US concerning the (un)constitutionality of the Armed Career Criminal Act.  As federal sentencing fans should know, there seem to be a real chance that Justice Scalia will convince enough of his colleagues to strike down ACCA as unconstitutionally vague.

Helpfully, Leah Litman has already authored an article, "Residual Impact: Resentencing Implications of Johnson v. United States’ Potential Ruling on ACCA’s Constitutionality", about some of the legal issues that might follow from a big constitutional ruling in Johnson.  But the question in the title of this post is focused on the practical question of just how many current federal prisoners serving ACCA sentences of 15 or more years could seek to benefit from ACCA.  

This helpful new "Quick Facts" report from the US Sentencing Commission indicates that in Fiscal Year 2014 roughly 10% of 5,500 federal firearm offenders were sentenced under ACCA to an average sentence of 188 months in prison.  Assuming that these numbers are typical for firearm sentencing in each of the last dozen years, we can then extrapolate to estimate that there may be as many as 7,000 current federal prisoners serving ACCA sentencing term.

Critically, though, even if the Supreme Court were to declare ACCA's residual clause unconstitutionally vague, that ruling alone would not necessarily impact all (or perhaps even most) of current ACCA prisoners.  Sentencing judges in many (maybe most) cases sentenced under ACCA likely did not rely on the residual clause of the statute to find enough triggering prior offenses to require the application of the severe ACCA sentence.  Among the uncertainties which could flow from a big ACCA ruling in Johnson  is whether other parts of the ACCA statute and prior convictions based on other parts of the ACCA statute are still valid if one ACCA clause is struck down as unconstitutionally vague.

Some related prior posts:

• Terrific SCOTUSblog previews of this week's SCOTUS arguments in Johnson and Yates
• Based on questions asked at SCOTUS oral argument, wins predicted for federal defendants in Johnson and Yates
• SCOTUS orders new briefing and argument on ACCA's constitutionality in Johnson!?!?!
• "Residual Impact: Resentencing Implications of Johnson v. United States’ Potential Ruling on ACCA’s Constitutionality"