What exactly does &quot;It is a defense to prosecution&quot; mean?
<p>Consider the Texas Child Safety Laws found here: <a href="https://statutes.capitol.texas.gov/Docs/TN/htm/TN.545.htm#545.412" rel="nofollow noreferrer">https://statutes.capitol.texas.gov/Docs/TN/htm/TN.545.htm#545.412</a></p>

<p>It says in one place: </p>

<blockquote>
  <p>(c)  It is a defense to prosecution under this section that the person
  was operating the vehicle in an emergency or for a law enforcement
  purpose.</p>
</blockquote>

<p>And a little lower it says:</p>

<blockquote>
  <p>(b)  It is a defense to prosecution of an offense to which this
  section applies that the defendant provides to the court evidence
  satisfactory to the court that:</p>
  
  <p>(1)  at the time of the offense:</p>
  
  <p>(A)  the defendant was not arrested or issued a citation for violation
  of any other offense;</p>
  
  <p>(B)  the defendant did not possess a child passenger safety seat
  system in the vehicle; and</p>
  
  <p>(C)  the vehicle the defendant was operating was not involved in an
  accident; and</p>
  
  <p>(2)  subsequent to the time of the offense, the  defendant obtained an
  appropriate child passenger safety seat system for each child required
  to be secured in a child passenger safety seat system under Section
  545.412(a).</p>
</blockquote>

<p>Is "it is a defense to the prosecution" something that just suggests that the judge may, at his or her discretion, rule in favor of the defendant when s/he meets the conditions, or is this saying that the defendant, under the law, should definitely not be held guilty when proving these conditions were met?</p>

<p>In the first example, I would expect the defendant to be not guilty even if brought to court on multiple occasions. In the latter example, I would assume the defendant would only be let off the hook the first time but that s/he would be guilty in subsequent cases.</p>

<p>So to me common sense dictates that "it is a defense to the prosecution" is not a binding  statement that requires the defendant be let off the hook but rather than it's at the discretion of the judge, but I just wanted to verify that this is accurate.</p>

<h2>A “defense to prosecution” is a total <a href="https://en.m.wikipedia.org/wiki/Affirmative_defense" rel="nofollow noreferrer">affirmative defense</a></h2>
<p>If the defendant can prove (on the balance of probabilities) that the circumstances in the defense hold then they are not guilty.</p>

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