Motions for a New Trial Under Massachusetts Criminal Procedure Rule 30: A Comprehensive Guide
A motion for a new trial under Massachusetts Rule of Criminal Procedure 30 (Mass. R. Crim. P. 30) is a critical legal tool for defendants seeking to overturn their convictions after trial or guilty plea. Whether due to newly discovered evidence, constitutional violations, ineffective assistance of counsel, or prosecutorial misconduct, Rule 30 provides a mechanism to challenge a conviction and secure justice.
This blog post will explore:
What is a Motion for a New Trial Under Rule 30?
Legal Standards and Grounds for Filing a Rule 30 Motion
Key Procedural Steps in Filing a Motion for a New Trial
Burden of Proof and Judicial Discretion
Common Arguments in Rule 30 Motions
Recent Massachusetts Case Law on Rule 30 Motions
Practical Considerations for Criminal Defense Attorneys
1. What is a Motion for a New Trial Under Rule 30?
Massachusetts Rule of Criminal Procedure 30(b) states:
“The trial judge upon motion in writing may grant a new trial at any time if it appears that justice may not have been done.”
A Rule 30 motion allows a convicted defendant to challenge the validity of their trial or plea and request a new trial when fundamental fairness requires it. These motions are not appeals but post-conviction remedies designed to correct errors that affected the fairness or outcome of the case.
A judge may grant or deny the motion at their discretion, and the ruling can be appealed if denied.
2. Legal Standards and Grounds for Filing a Rule 30 Motion
A Rule 30 motion is not automatic—the defendant must establish a legal basis for why a new trial is warranted. The most common grounds include:
A. Newly Discovered Evidence
A defendant may seek a new trial if new evidence has surfaced that was not available at trial and could have altered the verdict.
To succeed, the defendant must prove:
✅ The evidence was not available at trial despite due diligence.
✅ The evidence is credible and not cumulative.
✅ The evidence is material and would likely have changed the jury’s verdict.
Example: DNA evidence exonerating a defendant convicted of murder.
B. Ineffective Assistance of Counsel
Under the Sixth Amendment and Article 12 of the Massachusetts Declaration of Rights, defendants are entitled to competent legal representation. If trial counsel was deficient and the errors prejudiced the outcome, a new trial may be granted.
Examples of ineffective assistance include:
🔹 Failure to investigate exculpatory evidence
🔹 Failure to object to inadmissible or prejudicial evidence
🔹 Failure to file motions to suppress unconstitutional evidence
🔹 Conflict of interest impacting defense strategy (see Commonwealth v. Fabian Beltran)
C. Prosecutorial Misconduct
A conviction may be overturned if prosecutors engaged in misconduct, such as:
Withholding exculpatory evidence (Brady v. Maryland violations)
Introducing false testimony
Making improper arguments that prejudiced the jury
Example: A prosecutor fails to disclose a key eyewitness’s contradictory statement, violating Brady v. Maryland and undermining the integrity of the trial.
D. Violation of Constitutional Rights
If the defendant’s due process, self-incrimination, or confrontation clause rights were violated, a new trial may be necessary.
Common violations include:
Denial of right to counsel
Involuntary confessions (Miranda v. Arizona)
Illegal searches and seizures (Fourth Amendment violations)
E. Errors in Jury Instructions
Improper jury instructions may mislead jurors, resulting in a wrongful conviction. A Rule 30 motion can be based on erroneous or omitted legal instructions that affected the jury’s understanding of the law.
Example: Failing to instruct the jury that the prosecution must prove intent beyond a reasonable doubt in a first-degree murder case.
3. Key Procedural Steps in Filing a Motion for a New Trial
Step 1: Drafting the Motion
The motion must be in writing and must:
✅ Clearly state the legal and factual basis for relief
✅ Include affidavits, transcripts, and other supporting evidence
✅ Cite relevant case law and legal precedents
Step 2: Filing with the Trial Court
The motion must be filed in the court where the conviction occurred. Unlike appeals, which go to higher courts, Rule 30 motions are first reviewed by the trial judge who presided over the case.
Step 3: Response from the Commonwealth
The prosecution has the opportunity to respond, often arguing that:
The motion is procedurally improper
The evidence is insufficient or immaterial
The original trial was fair and the verdict should stand
Step 4: Evidentiary Hearing (If Necessary)
A judge may grant or deny the motion without a hearing, but if substantial factual disputes exist, an evidentiary hearing may be required.
At the hearing:
🔹 Defense counsel presents witnesses, expert testimony, or new evidence.
🔹 The prosecution cross-examines witnesses and refutes claims.
🔹 The judge determines whether justice requires a new trial.
4. Burden of Proof and Judicial Discretion
The defendant has the burden of proving that a new trial is necessary. The standard is high:
The defendant must show that justice may not have been done (Commonwealth v. Lavrinenko, 473 Mass. 42 [2015]).
The judge has broad discretion to grant or deny the motion.
However, if a constitutional violation or an actual conflict of interest is proven, the court may grant a new trial without requiring proof of prejudice (Commonwealth v. Brown, 494 Mass. 326 [2024]).
5. Common Arguments in Rule 30 Motions
✔ “If this evidence was available at trial, the jury likely would have acquitted the defendant.”
✔ “Trial counsel’s failures deprived the defendant of a fair trial.”
✔ “The prosecutor’s misconduct undermined the integrity of the trial.”
✔ “The jury was improperly instructed on the law.”
6. Recent Massachusetts Case Law on Rule 30 Motions
✅ Commonwealth v. Fabian Beltran (2025)
🔹 Held: A defendant is entitled to a new trial if trial counsel had an actual conflict of interest, without requiring proof of prejudice.
🔹 Impact: Strengthened conflict-of-interest claims under Rule 30.
✅ Commonwealth v. Hallinan (2023)
🔹 Held: Defendants convicted based on faulty Alcotest 9510 breathalyzer results can seek a new trial.
🔹 Impact: Expanded grounds for OUI-related Rule 30 motions.
✅ Commonwealth v. Scott (2014)
🔹 Held: Prosecutors’ withholding of exculpatory evidence warranted a new trial.
🔹 Impact: Strengthened Brady claims in post-conviction relief.
7. Practical Considerations for Criminal Defense Attorneys
✔ Act Quickly – Rule 30 motions can be filed “at any time,” but sooner is better.
✔ Use Expert Testimony – Medical, forensic, or psychological experts can support newly discovered evidence claims.
✔ Be Strategic About Hearings – A well-drafted motion can sometimes win relief without a hearing.
✔ Anticipate the Commonwealth’s Arguments – Address procedural issues upfront to avoid dismissal.
Conclusion: Rule 30 Motions as a Vital Post-Conviction Remedy
A Motion for a New Trial under Mass. R. Crim. P. 30 is a powerful tool to correct injustices in the criminal justice system. Whether based on newly discovered evidence, ineffective assistance, or constitutional violations, these motions play a critical role in ensuring fair trials and protecting defendants’ rights.
For criminal defense attorneys, understanding how to craft a compelling Rule 30 motion can mean the difference between a client remaining incarcerated or securing a second chance at justice.