Top Five Tips for Effective Evidence Collection

By Kevin McManus, Chief Excellence Officer, Great Systems

Several years ago, I contributed a chapter to a John Wiley textbook on loss prevention engineering methods. My chapter focused on conducting effective incident investigations, which includes evidence collection. I also find that a lot of my TapRooT® root cause analysis course students often struggle with effectively collecting usable and necessary evidence. In recent years, I have continued to learn about what it takes to collect quality – necessary and usable – evidence in less time.

In this post, I want to share what I feel to be the top five tips for effective evidence collection. Such evidence can help solve problems and complete incident investigations. I have found that if you don’t collect the right evidence, you will compromise the rest of your problem solving process to some degree. How effective are your evidence collection efforts?

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How Effective are Your Evidence Collection Efforts?

Very few organizations measure the effectiveness of their investigation processes at all, let alone the crucial evidence collection step. With the use of traditional root cause analysis tools, such as the Five Whys, fishbone analysis, and/ or fault tree analysis, the failure of countermeasures to validate a given root cause represents a process failure. With the TapRooT® root cause analysis process, a lack of evidence results in missed opportunities to improve.

If you don’t have the evidence, it is difficult to justify the selection of each root cause. Do you gain the evidence through trial and error, testing countermeasure after countermeasure? When you improve your evidence collection efforts up front, it makes the weak or missing safeguards much easier to spot. How do your investigators know the best questions to ask? How effectively do your investigators spot the human factors concerns that affect the likelihood of human error each day?

Though quantitative evidence does not exist to prove it, I think it is safe to say that the quality of the evidence collection process drives the effectiveness of the root cause analysis process. Ultimately, evidence quality also affects the corrective actions investigation teams propose. An effective evidence collection process reduces root cause analysis process cycle time significantly, and also yields better results.

EXPLORE MORE: How to Measure Investigation Process Effectiveness

Tip #1 – Detect the causal factors you will analyze as early as possible

In the TapRooT® root cause analysis process, causal factors represent the equipment difficulties (failures) or human performance problems (errors) that require root cause analysis. With traditional root cause analysis approaches, causal factors are similar to process failures (non-conformances) that occur and produce defects. When we can find causal factors as early as possible in the investigation process, it helps to provide focus to the evidence collection effort.

Too much time is spent when we collect evidence that is interesting, but not really that necessary or useful, to the investigative effort. Valuable interview time, for example, is often lost when we explore the interesting, but largely irrelevant aspects of the problem’s story, even though time limitations exist. Try to define at least 2-3 preliminary causal factors early on to help focus the evidence collection effort on key problem areas.

Keep in mind that the definition of causal factors is an iterative process. Expect to re-word those factors you initially define, add a new one or two as your problem exploration reveals them, and possibly even drop one or two.

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Tip #2 – Utilize a pit crew approach to evidence collection

Imagine if only one person was allowed into the pit in motor sports to change tires, make suspension and engine adjustments, refuel the car, and clean the windshield. How long would it take to get in and out of the pit during a race? This example sounds silly, but all too often we expect one person to collect most, if not all, of the evidence for a given problem. Delays in evidence collection naturally lead to enhanced evidence erosion.

Engage multiple team members throughout the problem solving process if you want better results. To involve more people in your evidence collection efforts, everyone does not has to learn how to effectively interview others. Spread out the evidence collection workload through delegation to help collect more usable and necessary evidence in less time.

Certain team members can help tremendously when they quickly collect the right documents specific to the problem and organize them in a usable form for the investigation team. For example, have a team member quickly take great pictures at the scene for later analysis.  Such actions often represent a more effective use of time than rushing to conduct interviews.

Both of these tasks require a different skill set. When you match the best skills of each team member to similar evidence collection activities, you can collect more evidence in less time. An example ‘swim lanes flow chart’ for an investigation process can be found here. This flow chart format makes the roles that different people play in the effective execution of each process step clearly evident.

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Tip #3 – Use punch lists and question scripts to trigger evidence collection actions

What are your ‘key question triggers’? What prompts your investigators to ask the right questions? One of the main reasons investigators fail to collect the right amount of ‘necessary and usable’ evidence is that their questions are driven largely by only the design of the investigation form and their own past experience. Think about it. How do your investigators know the ‘right’ questions to ask when they investigate a problem? How do they know what to look for? What types of evidence should you expect?

For starters, include a well-rounded set of ‘starter’ questions on the problem definition, or incident investigation, form. Additional options exist to help investigators ask the key questions. Job aids, such as lanyard checklist badges and pocket cards, are one affordable choice. Soon, ‘heads up displays’ on our safety eyewear will give us such prompts. The goal remains the same though. Get better, and more, questions into the hands, and minds, of our problem investigators.

Tip #4 – Look upstream for initiating errors and stop / catch errors

At the start of the movie ‘Now You See Me’, there is a saying that sets the premise for this movie about magicians. It goes “the closer you look, the less you see.” One reason magicians are successful is that they distract you. They get you to look closely at things they want you to see. Magicians distract you from those things they don’t want you to see. Most investigators ‘get fooled’ when they focus primarily on the injured party or the most troublesome process step.

As a key step of the formal problem solving process, verify the degree that the problem solving or investigation team ‘looked upstream and downstream’ for contributing factors. The goal of any investigative effort should be to find and fix all significant system failures or gaps. Too many problem solvers focus on these errors that are closest to the most evident problem.

For example, what types of errors might have let the problem exist, or grow too large, in the first place? Did people miss opportunities to catch the error, such as inspection steps or hold points? When one invests time to look at a process problem, they should review the entire process for improvement opportunities. Don’t limit the analysis effort to only certain process steps or people.

LEARN MORE: Process Improvement Strategies

Tip #5 – Formally measure evidence quality with each problem solving cycle

Too few organizations measure the effectiveness of their investigation process, let alone their evidence collection efforts. The resources we invest in such efforts however are usually significant. Similarly, so are the potential consequences of ineffective corrective and preventative actions. In turn, we gain value when we formally measure the ‘vital signs’ of both the investigation process as a whole. Perhaps more importantly, we gain value when we measure the evidence collection effort itself.

Specific to evidence collection, one should formally assess the degree that investigators collect a complete evidence set. What percentage of our key questions did we adequately answer? How often did we collect evidence from all three sources – people, paper / screens, and place? How timely were each of our individual evidence collection efforts?

Also, you can use a five-point Likert scale, or simple ‘A-B-C’ grade assignments, to score the quality of the evidence you capture. For example, a simple ‘Pass / fail’ assessment could be made on each package of evidence you collect. To what degree did the evidence package meet the basic evidence collection criteria?

EXPLORE MORE: How to Measure and Improve Your Process Improvement Work System

How Can You Improve Your Evidence Collection Efforts?

As a contract TapRooT® root cause analysis process trainer, I see hundreds of investigations each year. I am confident that if you take advantage of the five evidence collection tips I define in this post, you will significantly improve your evidence collection process. If you have any questions, please do not hesitate to contact me at

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Keep improving!

Kevin McManus, Chief Excellence Officer, Great Systems

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