Expired Punishment
<p>If I commit a crime and many years later (> 25 years) send an email to the police claiming to have committed a crime, can they arrest me?</p>

<p>(assumming they do not think it is just a "prank email")</p>

<p>Severity of crime:<br>
Level 3 or 4 as defined by <a href="https://pap.georgia.gov/sites/pap.georgia.gov/files/CSL-s_Post_1-1-2006_considerations.pdf" rel="nofollow noreferrer">https://pap.georgia.gov/sites/pap.georgia.gov/files/CSL-s_Post_1-1-2006_considerations.pdf</a></p>

<hr>

<p>Some time ago, I took a criminology course and was told by the instructor that around 1000 people were known to have raped and/or killed Aboriginals in early/mid 1900 but were not sentenced since it "happened too long ago" (although there is evidence that the crimes have been committed)</p>

<p>Unlike the situation in the US where there are time limits to criminal prosecution, in Canada under <a href="http://laws-lois.justice.gc.ca/eng/acts/C-46/page-202.html#docCont" rel="nofollow noreferrer">Criminal Code 786(2)</a> the only limits are that "No proceedings shall be instituted more than six months after the time when the subject-matter of the proceedings arose, unless the prosecutor and the defendant so agree", for summary offenses. You have to look at the particular statute to determine if it is a summary vs. indictable offence. Persuading an RCMP officer to desert is a summary offence (<a href="http://laws-lois.justice.gc.ca/eng/acts/C-46/page-8.html#docCont" rel="nofollow noreferrer">§ 56</a>), but inciting to mutiny is an indictable offense (§53), for which there is no time limit on prosecution. I'm not aware of any state in the US with a statute of limitations on homicide, otherwise the limits vary. </p>

<p>The answer provided by user6726 is correct as far as it goes, but doesn't fully answer the following part of your question:</p>

<blockquote>
  <p>but were not sentenced since it "happened too long ago" (although
  there is evidence that the crimes have been committed)</p>
</blockquote>

<p>As user6726 notes, the barrier is not a statute of limitations. But, your question jumps the gun by noting that they "were not sentenced". What you really mean to say is that they <strong>were not prosecuted</strong> for and <strong>convicted of</strong> the crimes. Sentencing is a phase of the criminal justice process that happens only after a defendant is convicted of a crime.</p>

<p>To convict someone for a crime in criminal prosecution, you need to be able to prove guilt beyond a reasonable doubt and there are limitations on the extent to which hearsay evidence can be used in a criminal trial (or at least there was at the time). So, proof beyond a reasonable doubt of very old events in which physical evidence may no longer be available and some witness testimony may have become old or unreliable, may be a problem. Notably, one element that must be proved beyond a reasonable doubt is the subjective intent of the defendant (a.k.a. <em>mens rea</em>), which can be particularly hard to prove in a stale case.</p>

<p>Also, in Canada as in all countries derived from the English common law, prosecutors have a great deal of discretion in which cases to prosecute. They are not required to prosecute crimes simply because they have evidence, even rather strong evidence that they were committed. A prosecutor can decide as a matter of prosecutorial discretion not to press charges in stale cases even if the prosecutor has the legal authority to do so. </p>

<p>Prosecutors are particularly disinclined to pursue criminal prosecutions when the defendants are elderly and have been law abiding for decades, and when many similarly situated people lived their entire lives and died without being prosecuted. Some of the defendants in cases like these may even have dementia and may not even remember themselves what they did in their youth.</p>

criminal-law canada