Defense Engineer Says Your Injury Is Degenerative? Bonilla-Acosta v Max Services (2026)

On October 14, 2026, the Appellate Division, Second Department decided what a defense biomechanical engineer may tell a court about a car accident victim’s spine. The engineer was qualified to say whether the crash generated enough force to cause the injuries. The engineer did not show he was qualified to give the medical opinion that the injuries were degenerative. This office was not involved in the case. If the serious-injury rules are new to you, start with our guide to New York’s serious injury threshold.

Take one person through this. A delivery driver is rear-ended at a light on Hempstead Turnpike in Levittown. The neck pain starts that night, and the MRI shows a herniated disc. Months later the defense serves two reports: a radiologist who calls the disc degenerative, and a biomechanical engineer who says the crash was too gentle to hurt anyone. This decision tells that driver which of those reports is doing which job.

What the Second Department decided

The plaintiffs, Francis Bonilla-Acosta and Dinaili Andujar-Martinez, sued Max Services Corp. and Marco Miranda, among others, for personal injuries from a motor vehicle accident. Those two defendants moved for summary judgment on the serious-injury threshold. Supreme Court, Queens County (Ulysses B. Leverett, J.) denied the motion in an order dated May 8, 2025. The Second Department (Barros, J.P., Wan, Golia and Goldberg Velazquez, JJ.) affirmed.

The court made three separate findings. Each one is a failure of the defense’s own proof, which matters because a defendant who moves first carries the first burden. Here is the decision in one card.

The first finding is the familiar one. Our write-up of Prado v Town/Village of Harrison, the decision the court cited for it, walks through why a defense motion without competent medical evidence on the claimed injuries fails before the plaintiff’s papers are read. The second finding is the one that matters for causation.

What a biomechanical engineer can and cannot say

A biomechanical engineer is not a doctor, and the courts have not treated that as disqualifying. In Vasquez v Coastal Charter Serv. Corp., 240 AD3d 822 (2d Dept 2025), the Second Department wrote that “biomechanical experts are qualified to render opinions on causation,” and an engineer’s affidavit that the accident “did not generate sufficient force to cause the alleged injuries” won the defendants dismissal. Our 2014 write-up on an engineer allowed to testify covers an earlier First Department decision in the same direction.

Bonilla-Acosta does not retreat from Vasquez. It quotes it. The engineer, Richard A. Bandstra, “demonstrated that, based on his skill, training, education, and experience as a biomechanical engineer, he was qualified to render an opinion as to whether the accident could have generated enough force to cause the plaintiff[s’] injuries.” The problem was what else was in his reports. His opinions “were based, in part, on his conclusions that, based upon his review of the plaintiffs’ medical records, the alleged injuries to the cervical and lumbar regions of the plaintiffs’ spines were due to degenerative conditions and not causally related to the accident.”

That is a medical conclusion. The court held that he “did not demonstrate that he was qualified to render a medical opinion as to causation,” citing Martinez v Quintana, 138 AD3d 791 (2d Dept 2016). Martinez is a malpractice case about a radiologist, not an engineer; the rule it stands for is general. In Martinez, the court held that a radiologist qualified to criticize a missed fracture “established no foundation for his opinion with regard to the proximate cause of the plaintiff’s alleged injuries, which were orthopedic in nature.” An expert has to be qualified for the specific opinion given.

So the line runs through the middle of a single report. Consequently, the question to ask about any engineer’s report is not whether the engineer is qualified. It is which sentences are physics and which are medicine.

“A biomechanical expert can discuss how an accident can cause or not cause strains, sprains and other disc injuries.”

So when the defense hires their biomechanical engineer and sends the report, read what it actually says. The engineer can comment on force. The engineer is not a doctor. So if the report states that your injuries are degenerative because the engineer looked at your medical records, that’s a medical opinion. The engineer has to be qualified to give you that opinion. And then if the report throws out your deposition testimony of how you were injured, the report is not based on the facts in the record. So in essence, that report does not make the defense’s case.

Why the plaintiffs’ deposition testimony mattered

The court gave a second reason. The engineer’s “conclusions were based, in part, on his rejection of the plaintiffs’ deposition testimonies as to how their injuries occurred.” For that the court cited Cassano v Hagstrom, 5 NY2d 643 (1959), a Court of Appeals decision from a dental malpractice case. Cassano states the rule this way: “It is settled and unquestioned law that opinion evidence must be based on facts in the record or personally known to the witness.” The expert “cannot reach his conclusion by assuming material facts not supported by evidence.”

A biomechanical analysis typically starts from a version of the crash: speeds, positions, the direction of the hit, how the occupant moved. When the engineer picks a version the sworn testimony contradicts, the output inherits that choice. The court treated the rejection of the plaintiffs’ account as a defect in the opinion’s foundation.

Consequently, your deposition testimony is evidence the defense expert has to work with, not around. Describe the crash and the onset of pain precisely, and read the engineer’s assumptions against what you said under oath.

When the degeneration opinion comes from a doctor

Two weeks before Bonilla-Acosta, the First Department showed the other side of the line. In Gersic v Kuehner, 2026 NY Slip Op 05474 (1st Dept Sept. 29, 2026), the defense expert was a physiatrist, a physician. The court held the defendant “established prima facie that plaintiff’s claimed injuries were not causally related to the accident, but were in fact the result of chronic, preexisting degenerative conditions.” The burden then moved to the plaintiff.

The plaintiff’s treating chiropractor could properly tie the onset of symptoms to the accident, because the plaintiff reported no symptoms before it. That was not enough. The court wrote that the chiropractor “did not explain why plaintiff’s claimed herniations were traumatic in origin, as opposed to being degenerative in nature,” and “did not opine that the accident activated, aggravated, or exacerbated plaintiff’s degenerative conditions.” The orthopedic surgeon’s opinion had “the same defect.” The complaint was dismissed against both defendants.

Read together, the two decisions do not conflict. Bonilla-Acosta is about who may make the degeneration argument. Gersic is about what the plaintiff must answer once a qualified physician makes it. The First Department’s earlier decision in Osorio v Punjab Enter. Inc., 215 AD3d 494 (2023), shows both halves: a radiologist and an engineer together met the defense burden on the neck, and the plaintiff’s own radiologist and treating physician raised an issue of fact in response. Her knee claim was dismissed because her “expert failed to explain why the preexisting conditions documented in plaintiff’s medical records were not the cause of her symptoms.”

In practice, an engineer’s force opinion can still meet the defense burden, as it did in Vasquez; what Bonilla-Acosta removes is the engineer’s own degeneration reading. When a qualified physician supplies that reading, as in Osorio and Gersic, the plaintiff’s experts have to answer it.

What this means for your case

“In order to determine whether or not an injury is caused by an accident, the defendant who’s usually utilizing these experts would need a medical doctor.”

You do not argue causation; your doctors and your lawyer do. What you control is the record they will work from. Our hub on pre-existing injuries covers the aggravation rules in more depth.

So let’s go back to our hypothetical example where you’re rear-ended, your neck hurts and the MRI shows a herniated disc. Well, you can expect that the defense radiologist is going to read every MRI as degeneration. And so what your doctor needs to do is address causation directly and indicate why these findings are traumatic rather than degenerative. So tell your doctor how the accident occurred, right? Tell your doctor whether or not your neck ever bothered you before. If it never did, that has to be in the records.

Keep treating, or keep a record of why you stopped. In Holmes v Brini Tr. Inc., 123 AD3d 628 (1st Dept 2014), an unexplained “complete cessation of all treatment” was held to interrupt “the chain of causation” and render a permanency finding speculative. Our post on gaps in treatment explains how that plays out.

Bring these to the first call:

• the police report or accident report number, and photographs of both vehicles;
• every MRI and X-ray report, with the dates, and the name of the radiologist who read each one;
• the names of any doctor, chiropractor or physical therapist you saw for the same body part before the accident, or a plain statement that there were none;
• your deposition transcript, if one has been taken, and any defense medical or engineering report you have been served.

A checklist for referring lawyers: building causation proof

For the lawyer who referred the case or is still handling it, the two decisions translate into the file this way. Each line traces to an opinion quoted above.

I used to write the causation argument for insurance carriers. The carrier would come forward with proof that the injury was a result of a pre-existing condition and not traumatically related. Therefore, the burden shifted to the injured person. That argument only worked as well as the medical proof that supported it. If the proof is an engineer’s medical opinion about a disc, then the burden does not shift.

That is my view of how the decisions fit together. The appellate courts will keep refining where an engineer’s opinion ends and a physician’s begins.

Which version of the serious-injury law applies

The third finding carries a phrase every New York injury lawyer should notice. The court measured the 90/180-day category under “the version of Insurance Law § 5102(d) in effect at the time the plaintiffs commenced this action.” Part EE of chapter 58 of the Laws of 2026 amended § 5102(d) and deleted the category for a “medically determined injury or impairment of a non-permanent nature” lasting “not less than ninety days during the one hundred eighty days immediately following the occurrence.” Section 4 of Part EE provides that the act “shall take effect immediately and shall be applicable to all actions and proceedings commenced on or after such date,” and it took effect May 26, 2026.

This action was commenced before the reform (the order on appeal is dated May 8, 2025), so the older definition, with nine categories, governed. A case commenced on or after May 26, 2026 is measured against the eight that remain. Consequently, the filing date of the summons and complaint, not the accident date, is the first thing to check when reading any threshold decision. Our threshold guide lists the current categories.

Sources

• Bonilla-Acosta v Max Servs. Corp., 2026 NY Slip Op 05928 (2d Dept Oct. 14, 2026)
• Gersic v Kuehner, 2026 NY Slip Op 05474 (1st Dept Sept. 29, 2026)
• Vasquez v Coastal Charter Serv. Corp., 240 AD3d 822, 2025 NY Slip Op 04270 (2d Dept 2025)
• Osorio v Punjab Enter. Inc., 215 AD3d 494, 2023 NY Slip Op 01963 (1st Dept 2023)
• Prado v Town/Village of Harrison, 244 AD3d 884, 2025 NY Slip Op 06881 (2d Dept 2025)
• Martinez v Quintana, 138 AD3d 791 (2d Dept 2016); Holmes v Brini Tr. Inc., 123 AD3d 628 (1st Dept 2014); Cassano v Hagstrom, 5 NY2d 643 (1959)
• Insurance Law § 5102
• Laws of 2026, chapter 58, Part EE (A10008-C)