Cross-Border Evidence & MLA: Ensuring Admissibility in Court

Obtaining evidence from abroad through Mutual Legal Assistance (MLA) is a major achievement. However, the final and most critical test occurs in the domestic courtroom. Often, judges view evidence gathered by foreign authorities under different legal systems with caution. Furthermore, the chain of custody can stretch across long distances, and collection methods may not match local procedural rules exactly. Therefore, ensuring the admissibility of cross-border evidence becomes an essential skill for every prosecutor and defense attorney.

This 2025 guide focuses squarely on the last step of the MLA process: converting foreign-obtained evidence into proof that a judge or jury can legally consider. Specifically, we will explore common legal hurdles, emphasize the vital role of proper certification, and outline strategic approaches to defeat defense challenges. Ultimately, whether you present bank records from Switzerland or a witness statement from Singapore, this guide will help you build a rock-solid foundation for admissibility in court.

🚧 Common Hurdles to Admissibility of Cross-Border Evidence

You must understand potential objections to preempt them effectively.

The Hearsay Rule: This is the most frequent challenge. Documents like business records or witness statements from abroad are “out-of-court statements.” Courts may exclude them as hearsay without a valid exception.
Authentication Problems: Opposing counsel may argue you failed to prove the evidence is genuine. Is this document really an official bank statement?
Broken Chain of Custody: For physical evidence, the defense can challenge whether anyone tampered with it during its international journey. Gaps in the chain create reasonable doubt.
Violation of the Requesting State’s Laws: If the requesting state illegally obtained the evidence, courts may exclude it as “fruit of the poisonous tree,” even if the foreign collection was legal.
Violation of the Requested State’s Laws: Evidence gathered through a grave breach of the requested state’s laws may lead to exclusion on public policy grounds.
Right to Confrontation: The U.S. Constitution’s Sixth Amendment and similar principles guarantee the right to cross-examine witnesses. A written statement may face challenges if the witness is unavailable.

📜 The Foundation for Admissibility: Certification and the MLAT Treaty

The MLA treaty and its accompanying certification provide the strongest tools to overcome these hurdles.

The Certificate of Authenticity (or Certification Letter):
This document is your cornerstone for admissibility. The Central Authority or judicial authority of the requested state issues it. A proper certificate must:

Attest to the authenticity of the documents.
Describe the legal process for obtaining the evidence, confirming compliance with local laws.
Carry the signature and seal of an authorized official.

Treaty Provisions as a Hearsay Exception:
Critically, many modern Mutual Legal Assistance Treaties (MLATs) contain a specific clause. This clause states that evidence produced in response to a request is admissible in the requesting state’s courts after authentication. Therefore, this treaty provision can act as a powerful statutory exception to the hearsay rule.

Example: Many U.S. MLATs state that evidence is admissible “without any further authentication” with the correct certificate.

🛡️ Proactive Strategies to Secure Admissibility

Admissibility is not an afterthought; it must be built into the MLA request from the beginning.

1. Draft the MLA Request with Admissibility in Mind:

Specify the Form of Evidence: In your Letter of Request, explicitly ask for a certificate of authenticity that complies with the relevant treaty article.
Request a Manner of Proof: If you need a witness statement to be admissible, ask for it to be taken under oath in a manner that resembles a deposition (e.g., with the opportunity for the defense to submit questions in advance).

2. Meticulously Manage the Chain of Custody:

Document every transfer of physical evidence, from the foreign authority to your Central Authority, and finally to your evidence locker. Use a chain-of-custody form.

3. Consider the “Under Seal” Procedure for Sensitive Evidence:

In some cases, you can request the foreign court to take evidence “under seal,” meaning the defense will not have access until a judge rules on its admissibility, protecting sensitive investigative details.

4. Be Prepared for a Daubert or Expert Challenge:

If the foreign evidence requires interpretation (e.g., complex financial records from a foreign bank), be prepared to qualify an expert witness to explain it to the jury.

⚔️ Responding to Defense Challenges: A Practical Guide

When a challenge is raised, be prepared with these arguments.

Against a Hearsay Objection:
- “Your Honor, the evidence is offered under the ‘public records’ exception to the hearsay rule, as it is an official document from a foreign government agency.”
- “Furthermore, the MLAT between the United States and [Country], Article X, specifically provides for the admissibility of such certified records.”
Against an Authentication Objection:
- Present the Certificate of Authenticity from the foreign government. Argue that this certificate, under the treaty and relevant evidence rules, is sufficient to authenticate the documents.
Against a Confrontation Clause Objection (for witness statements):
- If the witness is unavailable, argue that the statement bears sufficient “indicia of reliability” because it was taken under oath by a foreign judicial officer, following proper legal procedures.
- In some cases, use video conferencing to make the witness available for live cross-examination.

🌍 Country-Specific Considerations

Evidence from EU Member States: The European Investigation Order (EIO) framework standardizes the process, and evidence gathered under an EIO is generally admissible in other member states without further formalities.
Evidence from Common Law vs. Civil Law Countries: Evidence from other common law countries (e.g., UK, Canada, Australia) may be more easily adaptable, as their legal procedures are similar. Evidence from civil law systems may require more explanatory testimony.

📋 Case Study: Securing Admissibility of Foreign Bank Records

Scenario: A U.S. prosecution for fraud relies on bank records from Germany.

The Strategy for Admissibility:

The MLA Request: The prosecutor’s request specifically cited the admissibility article (Article 12) of the U.S.-Germany MLAT and asked for a certification letter.
The Evidence Package: The received records were accompanied by a signed certificate from the German Federal Office of Justice, stating they were obtained pursuant to a valid request and were authentic.
The Court Challenge: The defense objected on hearsay grounds.
The Result: The prosecutor argued successfully that the MLAT treaty created a hearsay exception and that the German certificate authenticated the documents. The evidence was admitted.

❓ Cross-Border Evidence Admissibility FAQs

Q1: What if the MLA treaty doesn’t have an explicit admissibility clause?
You must rely on domestic evidence law. The foreign certificate will still be strong evidence for authentication, and you can argue for hearsay exceptions like “business records” or “public records.”

Q2: Can the defense call the foreign official who signed the certificate to testify?
In theory, yes, but it is highly impractical. Courts are generally reluctant to require this, as it would cripple international judicial cooperation. The certificate is usually deemed sufficient.

Q3: What about evidence obtained without an MLA treaty?
Evidence obtained through other means (e.g., direct cooperation between police agencies) is still potentially admissible, but the proponent will have a heavier burden to prove authenticity and overcome hearsay objections without the treaty’s procedural safeguards.

Q4: How does this work for digital evidence?
The principles are the same. The key is obtaining a certification from the foreign authority that attests to the integrity of the digital evidence collection process (e.g., a hash value verification).

Q5: Can illegally obtained evidence from abroad be used?
This is a complex area. Generally, if the evidence was obtained illegally by the foreign authorities (but in compliance with their own laws), it may still be admissible in the requesting state. However, if the illegality is extreme, a judge may exclude it on public policy grounds.

🧭 Conclusion: Building an Unassailable Foundation

The admissibility of cross-border evidence hinges on foresight and procedure. By drafting your MLA request with the end goal in mind, specifically requesting the proper certification, and understanding the legal framework provided by the treaty, you can confidently present foreign evidence in court.

A successful MLA process does not end when the evidence arrives; it ends when that evidence is successfully admitted and helps secure a just verdict.

For a refresher on the initial evidence-gathering process, read our guide on Evidence Gathering Abroad: Using MLA for Documents, Witness Statements & Asset Tracing. To understand the full timeline, see How Long Does Mutual Legal Assistance Take? Realistic Timelines in 2025.