Ryan Frantz
Interview Cues

Effective accident investigators and incident analysts must objectively report facts as they are observed. How can these facts be discovered, especially when they do not always obviously present themselves? Through practice, an investigator will pick up several cues during interviews that lend themselves to deeper probing.

Root Cause

You’ve read Dekker and the canonical blog posts, watched a few presentations where folks proselytize that There Is No Root Cause (TM). You feel this deeply and wish that others would as well. An interview isn’t the time to spread the word; it’s a time to actively listen. And when you hear an interviewee describe or declare the root cause, seize on this as an opportunity to ask better questions, especially to learn about their perspective.

Just as we know that a “root cause” is not the end of an investigation, but a a potential starting point, so it is in an interview. This is a chance to ask the interviewee questions like the following:

How did you come to understand that this is the root cause of the incident?

What factors did you see that may have contributed to, or existed in parallel, to this root cause?

Of those factors, describe which, if any, may have been sufficient to cause the incident on their own?

You know that any number of contributing factors are each necessary but only jointly sufficient to create the conditions in which an incident occurred, but your interviewee may not. When you hear “root cause”, reflect that language in better questions that can help them yield new insights.

Internally, you may chafe at that language; channel that energy into a productive set of questions.

Human Error

Tim was hasty in pushing that revert out to production.

Aki was overconfident in her actions.

It’s easy, given the power of hindsight, to pass judgment about what made sense to a person in the moments leading up to or during an incident. Knowledge and error flow from the same mental sources; only success can tell one from the other. When you hear statements like those above, you may be able to extract tacit knowledge from the interviewee:

What is a normal, or expected, cadence for pushing code into production?

How is code typically deployed?

How does one develop confidence around the given task?

Statements that seek to blame a person for their actions are ripe with “if it had been me”-type connotations. Probe for content you can use to contrast the interviewee’s expectations with the events that unfolded. That context will yield interesting insights and, likely, more good follow up questions.

A useful tool is to re-frame these questions in terms of success:

What would a successful operation look like in this situation?

Note that success is often possible despite conflicting or unclear information, instruction, and goals. Getting your interviewee to describe these obstacles and how they work through those constraints provides another valuable source of tacit knowledge. Use that information to better understand the perspectives of those that participated in an incident.


Under normal conditions, that traffic wouldn’t have made it through the firewall.

Gavin should have known better than to deploy that package.

As an investigator, you want to avoid using or writing counterfactuals. They only serve to describe an idealized reality fueled (and justified) by hindsight. Still, when you hear an interviewee confidently state a counterfactual, it is an opening to explore their mental model of the environment and conditions during an incident:

How would they describe “normal conditions”?

How were the conditions during the event different?

How did conditions during the incident lend themselves to traffic moving through the firewall?

How would you have deployed that package?

Questions like these can help the interviewee provide their perspective, how they “see” things in the course of their work. The answers can provide additional avenues to discover more.


Similar to counterfactuals, opinions shed light on a person’s mental model. Keep an ear out for statements like the following:

I don’t think we’re using this tool correctly.

We’re not taking full advantage of that service.

Their process is a waste of time.

Perhaps the interviewee has extensive experience with a tool or service. Ask questions to bring out their expertise. Once you get someone talking about something they know, they may not stop! You’ll uncover many interesting threads to pull on.