## Facts

- Pari Ahmadi sought neurological treatment after experiencing numbness and other symptoms consistent with a possible spinal cord lesion.
- A neurologist at The Neurology Center, P.A. (NC) ordered testing, including a vitamin B-12 blood test to rule out B-12 deficiency.
- NC sent Ahmadi’s blood sample to National Health Laboratories, Inc. (NHL), an independent laboratory, for the B-12 test.
- NHL committed an admitted methodological error and reported a normal B-12 level.
- NC and later treating physicians relied on the reported normal B-12 level and did not timely diagnose B-12 deficiency; Ahmadi’s condition progressed.
- Ahmadi was later diagnosed with B-12 deficiency at another medical center, but only after irreversible neurological damage had occurred, leaving her permanently paralyzed.
- Ahmadi sued NHL, NC, and a hospital for negligence/malpractice; the jury found NHL and NC negligent and causally responsible and awarded $10 million; the hospital was found not liable.
- Post-verdict, NHL and NC each sought indemnification and contribution from the other; the trial court denied indemnity and ordered each to contribute 50% of the judgment.

## Issues

1. Whether either NHL or NC was entitled to common-law indemnification from the other on the theory that its own negligence was only secondary or passive.
2. Whether one defendant’s negligence was a superseding cause that, as a matter of law, cut off the other’s liability.
3. Whether the trial court erred by requiring equal (50/50) contribution between NHL and NC.

## Decision

- The court affirmed the judgment and post-verdict allocation.
- Neither defendant was entitled to indemnification because both were independently negligent and directly contributed to the injury.
- Neither defendant established a superseding cause as a matter of law; reliance by physicians on laboratory results (and the continued effects of an erroneous result) was foreseeable.
- The trial court did not err in ordering equal contribution between NHL and NC.

## Legal Principles

- When multiple tortfeasors concurrently cause a single, indivisible injury, each may be liable to the plaintiff for the entire harm, with contribution governing allocation between defendants.
- Indemnity shifts the entire loss and is generally limited to situations involving vicarious/derivative liability or a special relationship; it is not available when both parties are active, independent tortfeasors.
- An intervening negligent act is not a superseding cause unless it is so extraordinary or unforeseeable that it breaks the chain of proximate causation; this determination is typically for the factfinder absent only one reasonable conclusion.
- Equal contribution among concurrent tortfeasors is permissible where the record does not compel a different allocation of responsibility.

## Conclusion

The court treated the laboratory’s erroneous reporting and the physicians’ negligent reliance and treatment decisions as concurrent causes of a single injury, rejected efforts to shift the entire loss through indemnity or superseding-cause doctrines, and upheld an equal contribution order between the jointly liable defendants.


Nat'l Health Labs., Inc. v. Ahmadi, 596 A.2d 555 (D.C. 1991)