Drug Crimes Center · Procedure Guide

If you were caught in an undercover investigation, first check whether it was lawful

As more drugs are traded online, investigators also approach suspects by concealing or disguising their identity. If the investigation stays within legal limits, the results are used as evidence, but if it was entrapment that drew in someone with no intent to commit a crime, the indictment itself has no effect.

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Key Points

  • Police officers may conduct non-disclosure investigations, approaching crime scenes, including online, without revealing their identity (Article 4-2(1) of the same Act).
  • If there are sufficient grounds to support suspicion of a crime and other investigation is difficult, identity-disguise investigations, in which officers take part in transactions under a false identity, are also permitted, but court approval is required in principle (paragraph (2) of the same Article and Articles 4-3 to 4-5).
  • Using evidence obtained through undercover investigation for purposes other than those prescribed by law is prohibited (Article 4-6).
  • Entrapment, where investigative agencies use deception or schemes to lead a person with no original intent into committing a crime, is unlawful, and the resulting indictment is invalid (Supreme Court Decision 2005Do1247, decided October 28, 2005).

1. Two special investigation methods

  • Non-disclosure investigation · Approaching crime scenes or offenders and collecting evidence without saying, or while denying, that one is a police officer. It is permitted when it is for investigating drug crimes.
  • Identity-disguise investigation · Creating false identity documents and using that identity to make contracts and transactions, going as far as possessing, buying and selling drugs. There must be sufficient grounds to suspect a crime and other means must be difficult, and court approval is required in principle.
  • Emergency identity-disguise investigation · In urgent cases it may begin before approval, but if approval is not granted within 48 hours it must stop immediately.

2. Standards for unlawful entrapment

The Supreme Court distinguishes between an investigation that merely provides an opportunity to a person who already had criminal intent and entrapment that uses deception or schemes to make a person without criminal intent commit the crime. The latter is unlawful and the indictment is invalid, so the court must render a judgment dismissing the indictment (Supreme Court Decision 2005Do1247, decided October 28, 2005). The court looks at points such as the following.

  • Who approached first
  • Whether there was repeated persuasion despite refusals, or exploitation of sympathy or personal ties
  • Whether the investigative agency or a collaborator arranged the source of the drugs or the funds
  • Whether there are signs that the person had been committing the same crime before

Whether there was entrapment can also be an issue when an informant worked with investigative agencies and encouraged the crime. The key is to secure the entire conversation record and reconstruct how the contact began and continued.

3. Features of investigations into online transactions

It is easy to assume that messengers like Telegram leave no trace, but when a seller or courier is caught, buyers are often traced through seized phones, data from virtual asset exchanges, and CCTV footage of drop locations. Purchases made months earlier can become the starting point of an investigation.

Frequently Asked Questions

The police approached me disguised as a seller, and I bought from them. Is that entrapment?
If you intended to buy drugs from the start and the officer only gave you the opportunity to deal, it is likely to be seen as a lawful investigation. If you had no such intention and gave in to persistent urging, you can argue that it was unlawful entrapment.
Can conversations from an undercover investigation be used as evidence in other cases?
Evidence from undercover investigations can be used only in the cases listed in the law, such as the investigation and prosecution of the drug crime that was the subject of the investigation and related crimes (Article 4-6).

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Written on the basis of Korean statutes in force (National Law Information Center, Ministry of Government Legislation) and court precedents as of October 20, 2026. Results may differ with amendments to the law or the facts of each case. This page is general information, not legal advice.

Written and reviewed by Attorney Dongwoo Shin — Ph.D. in Law; certified criminal law specialist and certified divorce law specialist registered with the Korean Bar Association. He handles each case personally from consultation to judgment. About the attorney →
Last updated October 20, 2026

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