Medical Malpractice Center · Case Type

When a Diagnosis Was Late or Wrong,
the Key Question Is "Would Earlier Detection Have Changed Things?"

Misdiagnosis cases ask not what the doctor did but what the doctor failed to do. The issues are whether the patient's symptoms and test values should have raised suspicion of the illness, and whether finding it sooner would have changed the outcome.

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Key Points

  • The standard for negligence is whether, given those symptoms and test results, the doctor should have suspected the illness and ordered further tests.
  • Causation is argued on whether there is a probability that an earlier diagnosis would have changed the course of treatment.
  • If the disease was already advanced or the prognosis was poor to begin with, courts often reduce the percentage of liability.
  • Test reports, imaging reports, outpatient and emergency room records, and records from the day a diagnosis was confirmed at another hospital are the core evidence.

Four typical situations

  • Late detection of cancer · When suspicious findings appeared at a checkup or outpatient visit but no detailed testing was recommended, or the imaging was misread
  • Being sent home from the emergency room · When chest pain, headache, or abdominal pain was dismissed and the patient was sent home, after which it developed into a heart attack, stroke, aortic dissection, or ruptured appendix
  • Test results left unattended · When a test was done but the results were not read or not communicated to the patient
  • Delayed transfer to a larger hospital · When transfer was delayed even though the patient's condition was beyond what the hospital could handle

How causation is proven

To show what would have happened if the illness had been found in time, you must support, with medical literature and expert opinion, how far the disease progressed during the delay and what difference that made to the chances of survival and the treatment options.

Where the burden of proof is eased · The Supreme Court presumes causation if the patient establishes two things. One is that there was an act that could be considered negligent under the medical standards of the time; the other is that it is probable that this act produced the outcome. However, the probability must be consistent with medical principles, and a mere possibility is not enough. If the hospital proves another cause, the presumption is broken (Supreme Court Decision 2022Da219427, decided August 31, 2023).

Documents to prepare

  • Outpatient and emergency room records : The symptoms reported, vital signs, the doctor's assessment, and the discharge instructions
  • Test reports and imaging reports : Whether abnormal findings were noted, and whether further testing was recommended
  • Records from the hospital that confirmed the diagnosis : The disease stage at the time of diagnosis and the treatment plan
  • Past health checkup results : Whether there were abnormal findings earlier, and whether you were told about them

Frequently Asked Questions

I was told at a checkup that nothing was wrong, but cancer was found a few months later.
You need to examine whether abnormal findings were already visible in the checkup imaging, and whether the reading was appropriate in light of the medical standards at the time. The first step is to obtain the original images and ask another specialist to read them again.
The emergency room sent me home saying it was indigestion, but it later turned out to be a heart attack.
The key is whether basic steps such as an electrocardiogram and cardiac enzyme tests were taken for a person complaining of chest pain, and whether the results were read correctly. Obtain the emergency room records and the times each test was performed.

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Written on the basis of Korean statutes in force (National Law Information Center, Ministry of Government Legislation) and court precedents as of October 20, 2026. Results may differ with amendments to the law or the facts of each case. This page is general information, not legal advice.

Written and reviewed by Attorney Dongwoo Shin — Ph.D. in Law; certified criminal law specialist and certified divorce law specialist registered with the Korean Bar Association. He handles each case personally from consultation to judgment. About the attorney →
Last updated October 20, 2026

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