Why “Human Error” Isn’t Enough for a Root Cause

“They forgot” leaves a question unanswered

An operator misses a step. Someone enters the wrong value. A required check is not documented. Calling the event “human error” may describe an action or omission, but the label alone does not explain how it happened or why the controls did not prevent or detect it.

That is the concern behind the phrase “human error isn’t a root cause.” Taken literally, though, the phrase goes too far. Human performance can be a supported causal finding. The goal is not to ban a category; it is to avoid using that category as permission to stop investigating.

A defensible conclusion identifies the specific failure, shows the evidence, considers other explanations, and explains the action decision. “Human error” without that reasoning is an incomplete explanation.

A value entered into the wrong field

Hypothetical example

During review, Quality finds that an operator entered a process value in the adjacent field of a paper record. The operator recalls being interrupted. It is tempting to write “operator distracted” and assign retraining.

First establish what the record and other evidence actually show. Was the process performed correctly? Is the original value recoverable from an independent source? Could the entry affect decisions about the batch? Follow approved correction and investigation procedures; do not treat recollection as proof of the original result.

Now test possible contributors. The fields may look alike, instructions may be unclear, or the interruption may have mattered. Each is a hypothesis. An awkward layout does not become the cause merely because it looks awkward, and an interruption does not establish causation simply because it occurred.

Look for evidence that could change your mind

Review the version of the instruction and record used at the time, training and qualification information relevant to the task, the sequence of work, and any available system or equipment records. Look for similar events and ask whether they point to a broader pattern.

Interview personnel to understand the work as it was done. Ask them to walk through the sequence, explain the cues they used, and describe where the process became difficult. Open questions are usually more informative than asking someone to agree that they should have been more careful.

Then challenge the preferred explanation. What would you expect to see if the layout contributed? Do other observations support or contradict that idea? If the evidence cannot distinguish between explanations, record the uncertainty instead of converting a possibility into a fact.

Accountability and system thinking can coexist

Looking at the surrounding system does not erase individual responsibility. It helps determine whether the proposed response addresses the conditions involved. A person can depart from a clear instruction while a separate process weakness also contributes to the outcome.

Do not invent a system cause to make a conclusion sound sophisticated. It is reasonable to conclude that evidence supports a specific individual error, provided the investigation justifies that finding and examines plausible procedural, process, and system contributors. More than one cause may be supported.

Equally, an absence of obvious equipment alarms or a completed training record does not, by itself, prove that the remaining explanation must be human error. A training signature establishes something narrower than demonstrated understanding of a particular task.

Retraining is an option, not an automatic answer

If evidence demonstrates a knowledge or skill gap, targeted training and an appropriate competence check may help. If the failure arose from ambiguous instructions, similar-looking fields, or a workflow that depends on memory, consider changes directed at those findings.

In the hypothetical example, a record-layout revision might help if the investigation supports a layout contribution. Assess the proposed change through the applicable quality process. Do not add a second check simply because it feels reassuring; consider whether it would detect the actual failure and whether it creates new difficulties.

Define how you will evaluate the result. Relevant indicators might include correct use of the revised record and review of similar entries, alongside whether staff can execute the intended workflow. Choose a justified scope and timing rather than borrowing an arbitrary acceptance threshold.

The practical test is straightforward: if the same conditions happened again, what evidence supports the belief that the action would help?

The regulatory nuance matters

EU medicinal-product GMP context: EudraLex Volume 4, Part I, Chapter 1, paragraph 1.4(xiv), explicitly addresses human error. It calls for justification of that finding after checking that process, procedural, or system problems have not been overlooked. It does not prohibit human error as a cause. The same paragraph recognizes that a most likely cause may need to be addressed when the true cause cannot be established.

United States, drug products within scope: 21 CFR 211.192 requires a thorough investigation of specified discrepancies and failures. It does not define a universal root-cause category or prescribe one investigation tool.

Check the framework applicable to your product and jurisdiction, including specific EU guidance for advanced therapy medicinal products. The interview questions and action examples in this article are practical recommendations, not a mandatory investigation script.