Why can courts refuse evidence?
<h4>The question</h4>
<p>Layman here. This question was inspired by <a href="https://law.stackexchange.com/questions/84088/ordered-to-unlocking-a-car-trunk-may-i-lawfully-refuse">this question</a> and random things I've heard/read over the years.</p>
<p>I'm quite confused by a concept that comes up again and again and which people seem to hold for self-evident. And that concept is that there is some evidence which a court will refuse to admit. And that confuses be because... well, there's evidence. It leads to the truth. Why aren't you taking it?!</p>
<p>It's very easy to come up with realistic examples where:</p>
<ul>
<li>There is a piece of evidence which is clearly and irrefutably shows that a person did something very bad (say, murder)</li>
<li>This evidence is for whatever reason &quot;not admissible&quot; (say, it was obtained illegally)</li>
<li>And there is no other piece of evidence that would incriminate this person.</li>
</ul>
<p>Does that mean that the perpetrator gets to go free? How can the court refuse to admit evidence, especially if it's the only useful evidence existing? And if yes, then why is this so and where is this practice useful?</p>
<hr />
<h4>Some examples from the top of my head</h4>
<p>The example question above deals with unlawful searches. Imagine that a police officer decided to search a car (or an apartment) and forcefully did so against the protests of the owner (or maybe the owner wasn't even present). They thought they might find drugs or something, but instead they are surprised to discover a dead body, clearly murdered. So... now what? According to the above question, since the search was illegal, this is inadmissible evidence in the court. Does that mean that the owner of the car/apartment gets to go away scott-free? Do they launch a new investigation and try to find other evidence <em>except</em> the fact that it was inside the property of this guy here (and failing to do that, release them)? If the owner of the car/apartment says &quot;I don't know what you're talking about, I last saw Jimmy here alive and well at the pub last night; I never seen his corpse before.&quot; - can they call him out on the obvious lie?</p>
<p>Or, another example. I don't know about USA, but here in Europe it's illegal to record someone's phone calls without a warrant (or something like that; it's serious). Any recordings obtained unlawfully will be inadmissible as evidence.</p>
<p>Let's now imagine that I've gone the full extra mile and have secretly bugged everything in my neighbour's house because I suspect (but have no evidence) that they murdered my child last month. I've got hidden cameras, microphones everywhere, etc. So one day I catch him talking to his spouse on the phone and mentioning the murder, admitting to doing it, and even telling where he buried the body.</p>
<p>Now I have evidence... or do I? I give the recording to the police, they search the indicated place and they do find the body, but since they cannot accept my recording as evidence... does that mean that my neighbour now has no consequences? Let's also suppose that no other evidence is found that would indicate his guilt (the guy was thorough). Obviously I'd get some grief for bugging my neighbour's house, but do I now also become the prime suspect in the murder of my own child? After all - the recording of my neighbour's confession &quot;officially doesn't exist&quot;, and I'm the one who told the police where to dig, so...</p>

<p>Different exclusionary rules have different reasons.</p>
<p>Hearsay is frequently inadmissible because it's less reliable for the court to hear Alice saying &quot;Bob told me that Carol hit him&quot; than to hear Bob saying &quot;Carol hit me.&quot;  Another even more critical problem with hearsay testimony is that the defense cannot cross examine the person who made the statement in court.  If Bob is there, the defense can ask questions such as &quot;where did Carol hit you&quot; and &quot;did Carol use her right or left hand&quot; to clarify the testimony or call its veracity into question.  Alice, not having been a direct witness to the act, will not be able to respond to many of these questions.</p>
<p><a href="/questions/tagged/united-states" class="post-tag" title="show questions tagged &#39;united-states&#39;" rel="tag" aria-labelledby="united-states-container">united-states</a></p>
<p>Evidence obtained in violation of a constitutional right is inadmissible because admitting it amounts to allowing police or prosecutors to violate people's constitutional rights in order to obtain convictions.  Not only does an unconstitutional search itself violate the rights of the person being searched, but so does the use of evidence acquired in such a search.  See <a href="https://en.wikipedia.org/wiki/Fruit_of_the_poisonous_tree" rel="noreferrer">Fruit of the poisonous tree</a> at Wikipedia and the cases linked therein, especially <a href="https://en.wikipedia.org/wiki/Silverthorne_Lumber_Co._v._United_States" rel="noreferrer">Silverthorne Lumber Co. v. United States</a> and <a href="https://en.wikipedia.org/wiki/Nardone_v._United_States" rel="noreferrer">Nardone v. United States</a>.</p>

<p>You need to ask <em>why</em> evidence gets excluded. For example evidence that was obtained by a search without a proper warrant. That's not excluded to protect criminals, it's excluded so that law abiding citizens are protected from having their home or their car or their body searched by a police officer. So first we have a law: A police officer is not allowed to search your home without a search warrant.</p>
<p>But what if they do? As a society, we want to prevent it from happening, and you prevent it by having punishment. However, if you punish police officers directly, you have the problem that a police officer is with one foot in jail all the time, so nobody wants to be a police officer. If we had a law that they get punished if they search your home and nothing against you is found, that would give a police officer very good reason to fabricate evidence to find. So the punishment is something that (a) any police officer dislikes and (b) that makes searching your home without a warrant pointless: And disallowing any evidence from such a search is something that any police officer dislikes, and makes them look for legal ways to find the evidence.</p>
<p>Comments: &quot;Trusting that the existing American systems for disciplining officers could reliably deter officers from violating citizens' right is also somewhat optimistic&quot;. Any search without warrant would end up in court, in front of a judge. Who would ask for the search warrant, there wouldn't be one, so the search was without warrant, so the police officer is in trouble. Now if you think police officers would come and search my home just to have an excuse to mess it up, that's outside this question.</p>
<p>Vilx: phoog explained the law. I tried to explain why the law is there and in that form and not another form.</p>
<p>All in all, it is a very simple rule (simple rules are easy to follow), it protects innocent people from searches without search warrant (because police officers would have zero motivation to perform such a search), and it doesn't protect people committing crimes <em>much</em> (because when a person has committed a crime, hopefully the police would be able to get a search warrant, while for a person not committing any crime this would be less likely).</p>

<p>TL;DR: The law against torture and unwarranted searches have the same base justification: to protect the guilty.  Why protect the guilty? Because if the law doesn’t protect the guilty, it won’t protect the innocent. As proven  by the fact that something other than the law was used to <strong>determine</strong> they were guilty.</p>
<p>Long version: Some “evidence” isn’t actually evidence.  Hearsay is the prime example of that, and it is excluded because while it appears to be evidence it’s actually not.  If Sally tells Jenny that she robbed the 7-11 the day before, that doesn’t even prove that Sally was in the same time zone as the 7-11 at that time, let alone that she actually robbed it.</p>
<p>Another example is confession under torture, is that evidence?  The accused was burned until he said what he was told to say, that may or may not have lead to other physical evidence, but can you trust that evidence? Is it evidence against the accused, or evidence against the person that burned him until he said what they wanted him to say?  Or was there someone else involved that told the torturer what to get the accused to say?</p>
<p>But you are probably thinking of the simple case of searching without a warrant, surely that is safe? Searching without a warrant is a crime, with multiple offenders, it is also a conspiracy to commit the crime. You want to trust the word of people who committed a crime and engaged in a conspiracy to commit a crime against a person to present evidence they supposedly found confirming the guilt of the person they are conspiring against?</p>
<p>So why not make it legal, then there’s no problem right? It’s not a crime, there is no conspiracy, everything is good, right? Except historically those in power have been quite willing to order their minions to make up evidence against those they deemed enemies, as well as having them tortured into confirming that the evidence was true.  Even if we suppose we have a better class of bad Powers That Be nowadays, that wouldn’t be willing to torture people, expecting them to not make up evidence against people that they HONESTLY (but carelessly) believe are guilty is most certainly factually wrong, proven by various court cases where they did just that to convict people they thought were guilty.</p>
<p>Throwing out illegally obtained evidence is the least we can do, because it’s generally not practical to punish the criminal’s who illegally obtained evidence as they deserve.  Why isn’t it practical? Because frequently it takes a law degree and several hours of study to come to the correct conclusion, and the cops don’t have that kind of time.  Also, it’s hard to tell the difference between didn’t care and didn’t know.  The appropriate punishment would be the same as the accused would face if convicted of the crime, and if you make it a capital offense to get it wrong, it’ll be a lot easier and safer for the cops to shoot someone they think is guilty in “self defense” than to try to collect the evidence.</p>

<p>The issue is that generally, evidence obtained without due process is <strong>inherently unreliable</strong>. For your first example, to legally get a warrant in many countries, you need to have to present a convincing argument that a crime was committed. In the case of searches, not needing to do so could easily allow for the planting of evidence on pretty much anyone. How could you know that the police officer hadn't knocked over a cyclist, thrown their body in the boot of the nearest person's car and &quot;just happened upon it&quot; later because they decided that the person might have drugs?</p>
<p>Unlike the example you give about police with guns making split second decisions, a search is a planned and coordinated act usually involving multiple people and other people not necessarily present may also be responsible for these actions (like a superior officer). As mentioned in another answer, to make sure justice is being served, it's also a better deterrent to enact a penalty that affects all parties and not just an individual or group of individuals.</p>
<p>With <em>any</em> evidence presented to a court, there has to be a level of trust that this evidence is legitimate. Obtaining it illegally undermines that trust because once someone has proven willing to break the rules to obtain it, how can you trust that they haven't broken the rules and invented it or tampered with it?</p>
<p>Your latter example is interesting because the difference here is that this evidence is submitted by a civilian. Depending on the circumstances, region and if there are checks you can make on the evidence's validity, it could still be deemed admissable. After all, if I were to rob a house and witness a murder, many countries would still allow me to take to the stand and give testimony (which <em>is</em> evidence). Me having committed a crime to see this doesn't change that. In the case of law enforcement recording people, the people retrieving and verifying its validity are the same, an obvious conflict of interest.</p>
<p>Either way, evidence not being admissable in a court of law wouldn't make you a suspect, it just means the police would have to find other evidence, and the location of a body might help provide enough so it would still be useful information for them.</p>

<p><a href="/questions/tagged/common-law" class="post-tag" title="show questions tagged &#39;common-law&#39;" rel="tag" aria-labelledby="common-law-container">common-law</a></p>
<blockquote>
<p>that confuses be because... well, there's evidence. It leads to the truth. Why aren't you taking it?!</p>
</blockquote>
<p>Firstly, because whether a piece of evidence actually leads to &quot;the truth&quot; is usually arguable. The parties will normally have different views on whether it does.</p>
<p>For example, someone saying something about what they saw/heard <em>is</em> evidence. But is the person to be believed? Are they available to repeat the evidence from the witness stand, or are only their <em>words</em> available (as heard/recorded by someone)?</p>
<p>And then, very importantly, the courts do not actually seek &quot;the truth&quot;. It's a common misconception that they do. Instead, they resolve the <em>dispute</em> between the parties.</p>
<p>So, rules have been worked out over the centuries as to how disputes are to be resolved. These include rules of evidence.</p>

<blockquote>
<p>Does that mean that the perpetrator gets to go free?</p>
</blockquote>
<p>Quite possibly, depending on the case.</p>
<blockquote>
<p>Why is this so and where is this practice useful?</p>
</blockquote>
<p>At some point it was decided that it's better to let some guilty people go free than to allow violations of constitutional rights in order to get convictions.</p>

<p>How can a court refuse evidence? Because there are clear rules as to how evidence can be obtained and how they can be entered into a trial.</p>
<p>It is worth noting that concept of justice is not just who did the crime must do the time. Justice for the victim is just as important as justice for the accused.</p>
<p>If police obtain evidence illegaly then it is for the sake of justice that, that evidence is excluded.</p>
<p>If that means an otherwise slam-dunk case gets thrown out then that is inline with justice being served not against.</p>
<p>Poor policing is not the accused problem. Nor should the system allow police to do whatever they like.</p>
<p>The blackstone ratio, being a cornerstone of legal thought in much of the west says... &quot;It is better that 10 guilty people go free than 1 innocent person suffer.&quot;</p>
<p>Our justice system is skewed to bring forth not guilty verdicts. As unpleasant as that view may be to victims of crimes. As disgusting it is when terrible crimes are not punished in a way that alleviates our need for revenge.</p>
<p>It is the system we have and a concept you will only truly appreciate when you get accused of a crime.</p>

<blockquote>
<p>How can the court refuse to admit evidence, especially if it's the only useful evidence existing?  And if yes, then why is this so and where is this practice useful?</p>
</blockquote>
<p>The rules of evidence define what is and isn't legally evidence, and what is and isn't admissible. These rules vary by jurisdiction, and may differ in civil and criminal law. As underlined by phoog in <a href="https://law.stackexchange.com/a/84102/25215">their answer</a>, you don't want to reward investigators who act above the law and violate your rights, and you don't want to give evidence credibility it has not earned.</p>
<p>Consider that in a jury trial, like criminal trials in the United States, the worst thing that can happen is that someone is wrongfully convicted because a jury was presented shaky evidence that influenced their judgement, even if they were told to ignore it. The second worst thing may be that the trial has to be redone because the jury's judgement was tainted by the evidence, making everybody lose precious time and money.</p>
<p>Conversely, in a trial by a professional judge, the judge knows the law and is better equipped to evaluate a piece of evidence. The risk of their judgment being influenced by wrongful evidence may be considered negligible since by definition a professional judge is trusted with their judgement and their ability to tell right from wrong, in a way individual jurors simply aren't.</p>
<p>This might explain why rules of evidence are much more stringent in the United States than in France, where illegally obtained evidence may be admitted. But even if admitted, you still have to show that the evidence is genuine, not tampered with, and actually shows the thing you say it shows, or else it has little value.</p>
<blockquote>
<p>I give the recording to the police, they search the indicated place and they do find the body, but since they cannot accept my recording as evidence... does that mean that my neighbour now has no consequences?</p>
</blockquote>
<p>The rules of evidence need not apply to a police investigation. If we presume your recording is inadmissible, it means it can't be brought to court. But the police isn't the judiciary (it is, in fact, the executive), and an investigation isn't a prosecution or defence.</p>
<p>Rules may vary, but generally inadmissible evidence can still be used in the course of an investigation. Suppose a police officer overheard someone talk about your neighbour and how they heard from someone that they buried a body in the forest. That would be woefully inadmissible evidence by itself (two words: objection, hearsay). However, it may give cause to the officer to grab a shovel and start digging.</p>
<p>If the police finds a body on the basis of your illegal recording, then they still find a body. The recording is essentially an anonymous tip, it can't be used in court, but the body you find thanks to it can be used, and you and your neighbour can definitely become a prime suspects in a homicide investigation.</p>
<p>In the unlikely event the investigation can't turn up any useful and admissible evidence and exhausts all possible avenues, then it would most likely be shelved until such time new evidence turns up. Without useable evidence, prosecution can't show guilt beyond a reasonable doubt, so there's no point in going forward.</p>

<p>Your question invokes fairness of outcomes, i.e. you perceive the system as more fair if it is more accurate in determining guilt versus innocence. In other words, <a href="https://en.wikipedia.org/wiki/Distributive_justice" rel="nofollow noreferrer">distributive justice</a>.</p>
<p>Another concept is fairness of process or <a href="https://en.wikipedia.org/wiki/Procedural_justice" rel="nofollow noreferrer">procedural justice</a>, i.e. the system is fair if everybody has to play by the same rules. If obtaining a wiretap was illegal, then we should not allow any recording into the courtroom, whether the recording was made or not. We should enforce that the &quot;no wiretap&quot; rule is followed to keep the playing field level, even if someone did make a recording.</p>
<p>Similarly, it can be argued that people don't have &quot;due process&quot; or &quot;equal protection under the law&quot; if the prosecution gets to break the rules of the legal system against some defendants and not others.</p>
<p>Under procedural fairness, I think there is also less of an assumption of an objective truth about guilt versus innocence. If you instead think about guilt or innocence as simply an outcome of a two-sided contest, you may see the importance that the contest have fair and consistent rules for all participants.</p>

<p>There are already plenty of other answers which address matters like why evidence might get thrown out, but I would like to point out that evidence that gets thrown out can still influence a trial. I raise this point because you exemplified a scenario wherein your child is murdered by a neighbor.</p>
<p>Specifically, witnesses cannot provide testimony that would contradict physical evidence that was prevented from being heard at trial because that would be perjury. For example, suppose a police officer conducted an unwarranted search of a drug dealer's car and found a kilogram of cocaine. Because the cocaine was found from a warrantless search, it will be excluded from trial.</p>
<p>If, for some reason, the prosecutor wants to proceed to trial they will do so without being able to present the kilogram of cocaine. But by the same note, the defense will not be able to put forth a witness who testifies that there were no drugs in the car at all at the time of the search because that would be perjury and an attorney who prompted a question to elicit that response could be guilty of suborning perjury.</p>

criminal-law evidence rules-of-court admissibility