Doctrine of fruit of the poisonous tree in criminal law

The fruit of the poisonous tree doctrine is a legal principle in criminal litigation that prohibits evidence obtained through illegal means or in contravention of law from being admissible in court as evidence. The doctrine is based on the idea that evidence obtained or derived via improper means such as an illegal search, seizure, illegal wiretap or torture is tainted, hence inadmissible in court.

It primarily discourages law enforcement agencies from using illegal methods of gathering evidence and as well safeguard the fundamental right of the people. The admissibility of illegally obtained evidence is subject to the applicable practice in different jurisdictions based on their legal systems. For this piece, will be considering United States, United Kingdom, China, and Nigeria.

The phrase ‘fruit of the poisonous tree’ is a metaphoric expression for a tree that produces tainted fruits. The method of collecting evidence is viewed as a tainted tree that produces tainted fruits. It is not enough to just dispose a piece of tainted fruit and pick another one from the tree; the entire tree is poisonous and nothing the tree produces can be safe to use.

The principle basically protects the citizens from illegal searches, involuntary confessions, and unlawful arrest. For example, evidence collected without probable cause, or a search without a warrant may be deemed tainted and, therefore, inadmissible.

The doctrine was judicially established by the decision in Silverthorne Lumber & Co. V. United States (1920), and the phrase‘fruit of the poisonous tree’ was coined by Frankfurter in his opinion in Nardone v. United States (1939) to describe illegally obtained evidence. The rule typically bars even testimonial evidence resulting from excludable evidence, such as an involuntary confession. Illegally or improperly obtained evidence is evidence obtained in violation of a person’s human rights or obtained in breach of the law or procedure and it would be unfair or unjust to use it.

In the United States, the exclusionary rule prevents illegal evidence from being used in court while the fruit of the poisonous tree doctrine prevents illegal evidence and all evidence that may stem from an illegal means from being admissible in court. An instance is if a law enforcement agent conducts an illegal search and collects evidence of a crime, the doctrine forbids the use of that evidence in court, as well as any evidence found legally if it stemmed from the illegal search. The fruit of the poisonous tree doctrine is important because it prevents prosecutors from using evidence that was collected through illegal means against the defendant.

The doctrine is applicable to all forms of evidence including oral and circumstantial evidence. For instance, a confession that is obtained after the Miranda warnings may be inadmissible if it is a product of an illegal arrest or police misconduct. Another example is evidence gotten via an illegal wiretap, not only is the tapped or recorded statement inadmissible, but real evidence also obtain through it are generally inadmissible.

There are generally four exceptions to this doctrine in the United States. In no order, the tainted evidence is admissible if there was an independent source: Evidence is admissible in court, if the prosecution can prove that it was obtained from an independent source from the original illegality.

Discovery was inevitable: If the prosecution can prove that law enforcement would have discovered the evidence eventually, whether or not they acted ultra vires, the evidence will be admissible. An example of this is the ‘attenuation doctrine’ where a law enforcement officer does not have a legitimate reason to stop someone but discovers that the person has an outstanding arrest warrant. If the officer arrests and searches the person, there is a good chance that any evidence the officer obtain will be admissible in court.

There was an intervening act of free will: An intervening act of free will by the defendant will break the causal chain between the evidence and the original illegal search and seizure and thus remove the taint. An example of this would be if a defendant was released on his or her own recognizance after an illegal arrest but later returned to the police station to confess. This voluntary act of free will removed any taint from the confessions.

The evidence was obtained in good faith:
If evidence is obtained illegally (defective search warrant based on no probable cause), but the police officer was operating in good faith (in a case where a judge signed the search warrant), then the evidence would not be excluded.

The United Kingdom: In contrast, England practices the inclusionary approach towards admissibility of evidence. All relevant evidence presented before the court is prima facie admissible. The rationale behind this approach is that the court considers the primary aim of the justice system to be the discovery of the truth and it is considered a priority above the protection of the accused’s right to private life. This primarily, favours the victim against the accused, nevertheless, the court retains the discretion to exclude prosecution evidence which lacks relevance to avoid miscarriage of justice.

The English case law distinguishes between illegally obtained real evidence and confessional evidence. Improperly obtained confession evidence, such as confessions obtained under torture contrary to Article 3 of European Convention of Human Rights (ECHR), can be seen as inherently unreliable. On the other hand, real evidence even if improperly obtained such as evidence obtained through searches or covert listening devices without a warrant, will remain reliable.

However, the courts in Scotland have in most proceedings excluded evidence illegally obtained. The Scottish court has expanded the practice of a discretionary rule and has moved towards the exclusionary approach to a unique Scottish model in which countries like Australia has adopted.

In China, the Criminal Procedural Law 2012 incorporated the exclusionary rules into China’s legal system. It adopted some new anti-torture procedures and laws, thereby legally prohibiting the police from forcing suspects either via threat or torture into incriminating themselves. This is essentially a significant improvement in the criminal procedural law of China as well as the country’s stance and commitment in the protection of human right.
At the same time emphasis is placed on the exclusion of oral evidence rather than physical evidence.

This approach imposes the burden to proof on the prosecution and require the police to give oral testimony in court to prove the legality of the evidence collection process when necessary. Unlike in the United States, the legislature’s aim is pursuing substantive justice over procedural justice.

In criminal proceeding in Nigeria, a fusion of the inclusionary and discretionary rule is practiced. By the provision of the Evidence Act 2011, all relevant evidence presented before the court is prima facie admissible on the one hand and on the other hand, the court may exclude evidence of facts which though relevant but appears to be too remote or the undesirability of admitting it outweighs the desirability of admitting it as evidence.

The provision of section 14, Evidence Act 2011 provides for the exclusion while section 15 provides guidance to the discretion of the court. This clearly shows that there is high reliance on the discretion of the court in determining the admissibility of evidence or it’s probative value in Nigeria.

In similitude of the England inclusionary approach, illegally obtained oral evidence in Nigeria such as involuntary confession is not admissible in court. The provision of section 29(2) and (5) of the Evidence Act 2011 made this clear. Confessions made forcefully out of threat of violence, torture, oppression, are not admissible.

In practice, the court will enter ‘trial within trial’ for the prosecution to proof that the confession (notwithstanding that it may be true) was obtained legally in the manner prescribed by the law. The burden of proof is always on the prosecution and the standard of proof is beyond reasonable doubt. This is also synonymous to the criminal procedural approach in China as it relates to illegally obtained oral evidence.

The contemplation of the Nigerian legislature is to eradicate inhumane treatment by law enforcement agencies. Predominantly, in the collection of evidence and to respect the fundamental human right of people in line with the chapter 4 of the constitution, the Anti-Torture Act 2017, and the Nigeria Police Act 2020.

In conclusion, the criminal procedural rules in each country have been developed in response to prevalent social issues, peculiar history, standard of police professionalism, court system, public attitude, adherence, and enforcement of law. The law reform in each country reflects the substantive need of the peculiar country thereby remodeling and advancing both the exclusionary rule and the inclusionary rule to suit their legislative needs.

For recommendation, countries where there are high cases of police brutality and low professional or operational standard of law enforcement agencies should embrace a flexible exclusionary model to pursue their stance in safeguarding the fundamental human right, law and order.

In Nigeria, for instance where there is high rate of police brutality, a bold legislative approach of not only excluding illegally obtained evidence but prescribing stricter punishment for erring officer will go a long way in establishing the country’s attitude towards safeguarding human rights. This will essentially discourage law enforcement agencies from engaging in illegal or reckless behaviours as a way to collect evidence.

Oluwatosin, a lawyer can be reached via [email protected]