The Missing Link Between What Happened and Why It Happened: Why Chronology Matters in Root Cause Analysis

In healthcare investigations, teams are often under pressure to identify causes quickly. Following a patient harm event, healthcare-associated infection, medication error, or near miss, the immediate question is usually, “Why did this happen?”

While well intentioned, this question can create a subtle but significant problem. Investigators may begin searching for causes before they fully understand what actually happened.

Cause-and-Effect Charting, also known as Causal Factor Charting, offers a different approach. Rather than starting with assumptions about causes, it starts with chronology. It reconstructs the sequence of events and conditions that existed before, during, and after an event. Only after the sequence is understood does the investigation move toward explanations of causation (Behrhorst et al., 2025; Rooney & Vanden Heuvel, 2004).

The distinction may seem minor, but it often determines whether an investigation uncovers meaningful system vulnerabilities or settles for superficial explanations.

The Common Mistake: Jumping Directly to Causes

Consider a healthcare-associated infection investigation. A patient develops a central line-associated bloodstream infection (CLABSI). During the initial review, staff identify that dressing documentation was incomplete. The investigation quickly concludes that documentation failures caused the infection. The problem is that the team may have identified a contributing factor without understanding the broader sequence of events.

Questions remain unanswered:

• When was the line inserted?
• Were there staffing shortages during the shift?
• Did the patient require multiple emergent procedures?
• Was dressing integrity compromised before documentation became incomplete?
• Were supplies available?
• Were there interruptions during line maintenance?

Without reconstructing the chronology, investigators risk confusing observations with explanations. A central principle of effective root cause analysis is that causes must be connected to events through an understandable chain of cause-and-effect relationships (Agency for Healthcare Research and Quality [AHRQ], 2024; Percarpio et al., 2008).

Events and Conditions: Two Different Pieces of the Story

One of the most valuable aspects of Cause-and-Effect Charting is its distinction between events and conditions.

Events

Events are actions or occurrences that happen at a specific point in time.

Examples include:

• A medication was administered.
• A catheter was inserted.
• A laboratory result was reported.
• A nurse responded to an alarm.
• A dressing change was delayed.

Events answer the question:

“What happened?”

Conditions

Conditions are circumstances that exist before or during events and influence how events unfold.

Examples include:

• Staffing shortages
• High patient acuity
• Missing equipment
• Inadequate training
• Workflow complexity
• Poor unit layout
• Excessive interruptions

Conditions answer the question:

“What was true at the time?”

Many investigations focus heavily on events while overlooking conditions. Yet conditions often explain why seemingly reasonable people make decisions that later appear problematic.

For example, “the nurse missed a dressing change” is an event. “The unit was operating with multiple float staff and unusually high patient turnover” is a condition. The event may be visible, but the condition often reveals the system vulnerability behind it (Behrhorst et al., 2025).

Why Timeline Reconstruction Reveals Hidden System Problems

A timeline is more than a list of activities. When events and conditions are arranged chronologically, patterns emerge that are difficult to see otherwise.

Investigators frequently discover:

• Escalating workload before an error occurred
• Communication breakdowns that developed over several handoffs
• Multiple barriers that failed sequentially
• Delays that compounded over time
• Organizational conditions that existed long before the event

Research and patient safety guidance emphasize that understanding the sequence of events is a foundational step in identifying meaningful causal factors and system weaknesses (AHRQ, 2024; Percarpio et al., 2008).

For example, an investigation into a delayed sepsis intervention may initially focus on a missed assessment. However, timeline reconstruction may reveal:

1. The emergency department experienced unusually high patient volume.
2. Boarding patients occupied treatment spaces.
3. Laboratory turnaround times increased.
4. Shift change occurred during patient deterioration.
5. Critical information was not communicated during handoff.
6. Recognition of sepsis was delayed.

The missed assessment becomes only one component of a larger system story. Without chronology, the investigation may have stopped at individual performance. With chronology, the investigation uncovers interacting system conditions.

Chronology Creates Stronger Causal Reasoning

One reason causal factor charting is valuable is that it forces investigators to demonstrate how causes connect to outcomes.

A cause cannot simply be asserted.

It must fit logically within the sequence of events.

For example:

Weak causal statement:

The infection occurred because staff were not compliant with policy.

Stronger causal chain:

• Supply shortages delayed dressing replacement.
• The dressing remained compromised for an extended period.
• The insertion site was exposed to contamination risk.
• The patient subsequently developed an infection.

The second explanation demonstrates chronology and causation.

This approach aligns with established rules of causation used in root cause analysis, which emphasize clearly showing cause-and-effect relationships rather than relying on vague labels or assumptions (Percarpio et al., 2008).

The Hidden Value of Looking Backward

Many healthcare investigations focus heavily on the period immediately preceding an event. However, some of the most important contributing conditions may have existed for weeks, months, or even years.

Examples include:

• Chronic staffing shortages
• Aging equipment
• Inadequate onboarding processes
• Poorly designed policies
• Inconsistent competency assessment
• Organizational normalization of workarounds

These conditions rarely appear in incident reports because they are not dramatic events. Instead, they become visible when investigators trace the chronology backward and ask what circumstances enabled the event sequence to occur. In many cases, the event itself is merely the final manifestation of a long-standing system weakness.

Moving Beyond Blame

Another benefit of chronological analysis is that it naturally reduces the tendency to focus on individual blame. When investigations begin with the question, “Who caused this?” attention often narrows to the person closest to the event. When investigations begin with, “What happened first, and what happened next?” attention broadens to the system. This shift frequently reveals that individuals were operating within conditions that increased the likelihood of error or failure. Rather than identifying a single person as the cause, the investigation uncovers how multiple events and conditions combined to produce the outcome (Behrhorst et al., 2025; AHRQ, 2024).

From Sequence to System Learning

Cause-and-Effect Charting is often described as a timeline tool, but that description understates its value. Its true strength lies in connecting chronology with causation. By distinguishing events from conditions, reconstructing the sequence of what occurred, and examining how factors interacted over time, investigators gain a deeper understanding of system performance. The result is not simply a better explanation of the past but a stronger foundation for preventing future harm.

Healthcare organizations frequently seek the cause before they understand the story. Yet the story is where causation becomes visible. The sequence matters because causation unfolds through time. Before asking why something happened, investigators must first understand what happened. Only then can the real causes emerge.

References

Agency for Healthcare Research and Quality. (2024). Root cause analysis. PSNet.

Behrhorst, J., Gale, B., & Van, C. M. (2025). The evolution of root cause analysis. PSNet, Agency for Healthcare Research and Quality.

Percarpio, K. B., Watts, B. V., & Weeks, W. B. (2008). How to perform a root cause analysis for workup and future prevention of medical errors: A review. Patient Safety in Surgery, 2(21), 1-9.

Rooney, J. J., & Vanden Heuvel, L. N. (2004). Root cause analysis handbook: A guide to efficient and effective incident investigation (3rd ed.). ABS Consulting.