Why does double jeopardy apply even when the acquittal was due to insufficiency of evidence?
<p>In the United States, the <a href="https://en.wikipedia.org/wiki/Double_Jeopardy_Clause" rel="noreferrer">Double Jeopardy Clause</a> of the U.S. constitution has been held to prohibit retrying a person for a crime they were previously acquitted of, even if the acquittal was merely due to an insufficiency of evidence.  To quote Wikipedia on the subject:</p>

<p>"Retrial is not possible if the verdict is overturned on the grounds of evidentiary insufficiency, rather than on the grounds of procedural faults."</p>

<p>The problem with this is, it is very easy to think of circumstances in which some, or even much, incriminating evidence might not come to light until after the trial (and possible acquittal).  One big category would be evidence only made useable by scientific and\or technological advances that hadn't yet happened at the time of the trial; for instance, DNA profiling, which could easily provide damning evidence against a suspect, was not available until the mid-1980s, meaning that there could potentially be any number of criminals running around from before then who couldn't be convicted at the time because evidence that would have been damning, had it been useable at the time, <em>wasn't</em> useable yet, because the techniques for using it simply didn't exist yet.</p>

<p>So why does double jeopardy prevent someone from being tried again, even if new incriminating evidence is found after the fact?  It would seem to me that the discovery of new evidence at a later date would serve as proof that the defendant <em>wasn't</em> fully in jeopardy in the earlier trial, since it would show that the prosecution was handicapped by not being able to use evidence that existed, but which had not yet come to light...</p>

<h2><a href="https://en.wikipedia.org/wiki/Double_jeopardy" rel="noreferrer">Double Jeopardy</a></h2>
<p>This is an ancient right that dates back to the jurisprudence of the Roman Republic when it was called <em>non bis in idem</em> (approximately - an issue once raised must not be raised again).</p>
<p>In its common law manifestation it applies to both civil and criminal trials and is an example that <em>one</em> of the functions of a judicial system is to bring <strong>finality</strong> to a dispute. This is often in conflict with the <em>other</em> aims of a judicial system which include <em>justice</em> and <em>efficiency</em>.</p>
<p>A <a href="http://www5.austlii.edu.au/au/journals/NSWBarAssocNews/2013/50.pdf" rel="noreferrer">speech</a> to the NSW Bar Association in 2013 by the then Chief Justice of Australia, <a href="https://en.wikipedia.org/wiki/Murray_Gleeson" rel="noreferrer">AM Gleeson AC QC</a> focused on finality and the following quotations illustrate why it is important:</p>
<blockquote>
<p>An acquittal by a jury is generally
conclusive. This is explained in terms of double
jeopardy. Autrefois acquit is a plea which, if made
out, defeats a prosecution. For a number of reasons
an acquittal may be regarded as erroneous. Later
evidence, such as a confession, or information based
on developments in technology, may suggest that an
acquittal was unsound.</p>
</blockquote>
<p>Double jeopardy is entrenched in the US Constitution and the <a href="https://en.wikipedia.org/wiki/International_Covenant_on_Civil_and_Political_Rights" rel="noreferrer">International Covenant on Civil and Political Rights</a> and the European Convention on Human Rights. The exact meaning varies: in many countries an acquittal at trial brings finality but others allow the prosecution to appeal an acquittal - this is not considered double jeopardy but rather a continuation of the same case.</p>
<p>That said, some countries (notably Australia and the UK) allow retrials after acquittal for serious crimes (murder, violent gang rape etc.) where there is &quot;fresh and compelling&quot; [NSW] evidence of guilt. These are 21st century changes and are a direct result of cases where advances in technology would impact the verdict.</p>
<p>As a constitutional protection, legislative change like this is not available in the United States.</p>
<p><a href="https://en.wikipedia.org/wiki/Geoffrey_Robertson" rel="noreferrer">Geoffrey Robertson AO, QC</a> in his 1998 book <a href="https://www.penguin.co.uk/books/1037628/the-justice-game/" rel="noreferrer">The Justice Game</a> says &quot;these rules are ordained by the State: whether they are just depends on whether they provide for the possibility of beating the State at its own game.&quot; His thesis is that, compared to <em>any</em> individual, the state wields unfettered power and has unlimited resources. If the state were allowed to repeatedly bring charges against an individual then they would eventually gain a conviction.</p>
<p><strong>The state gets one shot - they need to bring their A game.</strong></p>

<p>The reason is well summed up in <a href="https://supreme.justia.com/cases/federal/us/355/184/case.html#T4" rel="noreferrer">Green v. US</a>, 355 US 184, where the court says</p>

<blockquote>
  <p>The underlying idea, one that is deeply ingrained in at least the
  Anglo-American system of jurisprudence, is that the State, with all
  its resources and power, should not be allowed to make repeated
  attempts to convict an individual for an alleged offense, thereby
  subjecting him to embarrassment, expense and ordeal and compelling him
  to live in a continuing state of anxiety and insecurity, as well as
  enhancing the possibility that, even though innocent, he may be found
  guilty.</p>
</blockquote>

<p>This is a rule of the common law, established at least by 1676, and is enshrined in Blackstone's Commentaries which recognizes that</p>

<blockquote>
  <p>the plea of <em>auterfois acquit</em>, or a former acquittal, is grounded on
  this universal maxim of the common law of England that no man is to be
  brought into jeopardy of his life more than once for the same offence.</p>
</blockquote>

<p>So at least as long as you understand why there is a legal protection for the individual whereby the state cannot keep on trying and re-trying, it should be clear what this clause does. This is an instance of a more general principle of Anglo-American law, that the state, with all of its power, should be restrained from freely going after people.</p>

<p>The clause does not talk about "being fully in jeopardy", it simply talks about "jeopardy". There is always some evidence brought to bear on a case, which implies some risk (jeopardy); and it is never possible to have <em>all</em> of the imaginable evidence brought to bear on a case (which would be necessary to be "in full jeopardy"). If we can invoke the Double Jeopardy Clause only in a case where <em>all</em> imaginable evidence including that relying on currently nonexistent technology has been presented, then we can never invoke the clause.</p>

<p>Being prosecuted for a crime, even a minor crime, is costly and damaging.  Imagine there was no double jeopardy, and you were accused of disorderly conduct.  You go to trial, and the prosecutor presents no case other than a bare “there was an anonymous complaint, and Vikki was there”, jury finds you not guilty, prosecutor then has you arrested, saying they have found a new clue as to who anonymous was and you were still found at the scene, an by the way bail is the amount of the worth of your house.  The prosecutor may never figure out who complained and thereby get a witness that can resolve if you were actually acting disorderly, but you are still homeless or behind bars.</p>
<p>And that is assuming no actual malice or persecution by the authorities.  Imagine that there is actual malice, the charge is murder, and the “new” witness simply truthfully testifies that they weren’t there and didn’t see anything.  There are a whole lot of people that could testify they weren’t there and didn’t see anything while you remain behind bars or out on bail and under suspicion of being a murderer.</p>
<p>Double jeopardy means that if they have actual malice they must at least make up a new crime each time.</p>

evidence double-jeopardy