Lie Detector Tests in Germany: What Is Allowed in Court, at Work and in Private Life?

Is a lie detector test legal in Germany? In short: the test itself is not prohibited. What matters is who uses it, for what, and whether the person tested agrees voluntarily. This guide covers courts, employers and private use – factually, including the limits of the method.

Note: this article is general information and not legal advice. For your specific case, please consult a lawyer qualified in German law.

What a polygraph measures – and what it doesn't

A polygraph records physical responses – typically breathing, cardiovascular activity and skin conductance – while a person answers structured questions. It does not detect lies directly. A trained examiner interprets reaction patterns.

Two honest consequences:

• The result is a professional assessment, not proof.
• Nerves, health, medication or the way questions are asked can affect the outcome.

Lie detectors in court: not evidence in criminal proceedings

In German criminal proceedings, polygraph results play no role as evidence. The Federal Court of Justice (Bundesgerichtshof) ruled in 1998 (judgment of 17 December 1998, 1 StR 156/98) that polygraph examination is an unsuitable means of evidence in criminal trials – even when the accused volunteers for the test.

In practice:

• A test result does not replace evidence, witnesses or documents.
• Nobody can be forced to take a test.
• Anyone promising a "court-proof" polygraph result in Germany is promising something that does not exist.

When evidence is needed, the right people are lawyers, the police or, for private investigations, a licensed detective agency. DV Company does not offer detective work; our partner for this is AC Detective, a detective agency in Hamburg.

Employers: voluntary only, with written consent

An employer may not require employees or applicants to take a lie detector test. It intrudes deeply into personal rights and involves sensitive data. Employee data falls under §26 of the Federal Data Protection Act (BDSG) and Art. 88 GDPR.

Principles of responsible use:

• Voluntary: the person decides without pressure; refusing must have no consequences.
• Written consent in advance, explaining purpose, procedure and data handling.
• Specific purpose: a concrete question, not general screening of someone's life.
• Data minimisation: no questions about private life, health, religion or politics.
• No automatic decisions: no dismissal or rejection based on a test result alone.

Because employment is a relationship of dependence, genuine voluntariness is legally sensitive. Involve the works council (if any) and your data protection officer early, and have the setup reviewed by a lawyer.

How companies use a polygraph as a supplementary tool

Within these limits, companies use the polygraph as a supplementary tool:

• Hiring for positions of trust – voluntarily, alongside CVs, references and interviews.
• Regular checks of key staff – agreed in advance, with consent.
• Internal investigations – suspected data leaks, theft or irregularities.
• Suspected industrial espionage – often combined with a technical sweep of rooms, see bug sweeping.

Often the value lies in the structured interview: facts get clearer and innocent people get a fair chance to speak. The result is one piece of information among several – never the only one.

Details on our polygraph service for companies. Pricing depends on scope; you receive a quote in advance.

Private use: relationships and family

A private test between adults is not prohibited if both want it voluntarily – for example, over suspected infidelity. But:

• A test can open a conversation; it does not rebuild trust.
• Pressure undermines consent and makes the result meaningless.
• Do not rely on such a result in family court disputes.
• Secretly recording a partner is no alternative – it may be a criminal offence under §201 of the German Criminal Code.

Common mistakes

• Treating the result as proof.
• Pressuring employees into a test.
• Asking vague questions instead of concrete ones.
• Ignoring data protection – restrict access, set deletion periods.
• Overlooking technical causes: an information leak may come from a hidden listening device.

About DV Company

DV Company is based in Hamburg. Our founder Vadim Dischewski has worked in personal protection since 2008. Besides close protection we offer bug sweeping and polygraph examinations for companies. For an overview of protection pricing, see bodyguard cost.

Confidential first consultation

Considering a polygraph in your company? Book a free, confidential first consultation. We will tell you openly what the test can and cannot do.

Not legal advice.