How Mistakes Shape DF/IR Investigations

Every investigation hinges on one critical factor: human error. As a DF/IR investigator, your ability to spot and exploit those errors while avoiding your own is what separates success from failure, and you from your adversary. Let me show you how to turn mistakes into actionable leads, sharpen your analysis, and uncover the truth from my perspective and experience.

Human Error: The Foundation of Every Investigation

People make mistakes. Suspects* leave behind clues and have missteps and oversights in ways they rarely realize. Even when they know they’ve made a mistake, some mistakes cannot be undone, and they hope you don’t find those. Mistakes happen, whether suspects panic and try to cover their tracks or overestimate their cleverness. Either way, they leave a digital and physical trail if you know where to look. Your job is to see those mistakes for what they are: opportunities.

Success in this field does not come down to luck or flashy tools. That which seems to be luck is almost always just finding a mistake by being diligent in your analysis.? Good work creates "luck."

Unforced Errors

No suspect is as clever as they think they are. They reuse usernames, rely on the same email addresses across platforms, fail to consistently use VPNs, or forget about the metadata embedded in their files. Every one of these oversights is an opening for you to dig deeper.

For example, this suspect bragged online about getting away with a crime that made the local news. A mix of OSINT, subpoenas, and warrants found he’d reused an email address across another platform. That email was tied to a phone number used on another account. Eventually, I tied his fake usernames to a forum where he posted a picture of himself and used the same burner phone number on the account with his real name. That single photo gave me his face.? The account gave me his name.

When I seized his phone, the evidence corroborated everything. I found a video of him committing the crime, geolocation data, and connections to an unknown conspirator. What should have been a challenging case became straightforward because his arrogance got the better of him. Seems simple, but if you don’t look for the mistakes and errors, you will miss them.

Forcing Errors and Ethics in Investigations

Sometimes, the best way to catch a suspect is to create opportunities for them to screw up. Forcing errors involves creating a situation that causes suspects to act without thinking. A classic law enforcement tactic is “tickling the wire” during a wiretap (aka: electronic intercept, T3, or Title III). By leaking just enough information to the criminal organization or making a seemingly unrelated arrest, you can provoke a suspect into reacting by calling an accomplice, hiding evidence, or even making admissions over texts.

In a narcotic investigation, my partner called a drug manufacturer's phone, identified himself as a narcotics detective, to which the call ended.? It took less than 10 minutes before watching several people run out of the house, tossing evidence in a nearby river in plain view of us, resulting in multiple arrests, a search warrant, and the seizure of a truckload of evidence. Their mistake was leaving the confines of a home and running outside with armloads of plainly visible evidence because the police called to say hello...

The same idea works in digital investigations. Disrupting a suspect’s sense of control can make them scramble, leaving behind the very evidence you need. For example:

• Staged Communications: Investigators might let slip through various methods that they know a specific alias or account, prompting the suspect to delete it. These deletions leave behind metadata, timestamps, or logs that reveal critical clues.
• Simulated Legal Pressure: Serving a warrant or visible inventory of seized devices can prompt suspects to panic. In one case, an unknown suspect tried to delete files on secondary accounts we hadn’t yet identified, leaving an activity trail that confirmed their involvement.
• Decoy Devices or Data: Deploying monitored devices or decoy files can capture suspects attempting to manipulate or destroy evidence. This confirms their knowledge of the data and exposes their methods.

IMPORTANT: While effective, these tactics must be balanced with ethical considerations. You are responsible for upholding legal and professional standards, ensuring that actions are justified, proportionate, and within the boundaries of the law. Forcing errors should never cross into entrapment or privacy violations. A disciplined and ethical approach ensures evidence is admissible in court and maintains public trust in investigative practices.

Recognizing Your Vulnerabilities

Suspects aren’t the only ones who make mistakes. We are just as capable of a facepalm, and in this field, even one mistake can cost more than the case.

During my time undercover, I was tested constantly. Sometimes, suspects followed, confronted, or interrogated me to see if I was an informant. Staying calm and leaning into my role was more than just important, as one error could have ended the case or worse.

In DF/IR investigations, adversaries can test you in similar ways. They plant false evidence, manipulate data, or use tactics to waste your time. Validating every lead and questioning every assumption is vital to staying ahead and avoid falling into traps.

How to Spot Mistakes

Mistakes aren’t hidden; They’re sitting in plain sight, waiting for someone sharp enough to notice. Patterns and inconsistencies are often the biggest giveaways. Reused usernames, overlapping email addresses, and shared IP logins are excellent starting points. Metadata in files and emails can uncover everything from authorship to revision history, exposing evidence suspects hadn’t considered.

For example, I caught an attorney intentionally misleading the court in a civil litigation matter. A simple check of PDF metadata in multiple evidence files showed details contradicting the attorney's statements in filed motions. Whether it was arrogance or ignorance, it didn’t matter, as that 'oversight' became a pain point for the attorney in the trial.

Desperation also leaves a trail. Suspects who panic often rush to delete files, make sloppy edits, or forget to destroy evidence. Ironically, these actions can create more evidence than they erase. Sudden changes in behavior, unsolicited denials, or attempts to deflect attention are just as revealing. Their mistakes, when spotted, will often do half your work for you.

Ego: The Weakest Link

Ego is the single most significant liability in any investigation. Overconfidence blinds people to their vulnerabilities, whether they’re suspects or investigators.

I learned this the hard way. Years ago, I took an incredibly difficult training course and showed up unprepared, thinking my experience was enough. I failed. That experience taught me that ego does not replace preparation and discipline. Since then, I’ve never let my ego interfere with my work. Also, no failure has been due to a lack of preparation or effort.

Suspects rarely learn this lesson. Their arrogance drives them to reuse usernames, brag online, and underestimate the tools at your disposal. Their overconfidence leads to mistakes and eventual downfall, but only if you’re good enough to catch them.

Even when they know how they could get caught...

In 2012, a criminal hacker was caught because of EXIF metadata embedded in a photo posted online (Case Reference). That wasn’t the first or last time?hidden photo data exposed someone.

By now, you’d think everyone would know better. After all, it’s common knowledge that smartphones and cameras embed geolocation data in photos. Yet, criminals still make the same mistake.

Think it’s outdated? Think again. Just this week, authorities busted drug traffickers the same way: through photo metadata (CBS News Report).

?? The takeaway??The same?mistakes happen over and over again—if you’re aware enough to spot them.

Your Actionable Tips

• Look for Errors: Identify and exploit oversights like reused credentials, metadata, or logs.
• Force Errors: Create pressure that provokes suspects into exposing themselves, such as through staged communications or decoy data.
• Validate Everything: Stay skeptical and confirm every lead and assumption.
• Control the Narrative: Use psychological and investigative tactics to influence suspect actions while maintaining ethical discipline.

Final Thoughts

Mistakes are inevitable, but success depends on how you handle them. Whether it’s catching a suspect’s screwup or avoiding your own, discipline and attention to detail will always set you apart.?

The truth is always buried in human error, whether it’s arrogance, a rushed deletion, an unprotected login, or an overlooked artifact. Your job is to find it. Mistakes will always happen, but your ability to recognize and exploit them is what places the suspect behind the keyboard.

Brett's definitions

Error (noun) /?er-?r/

• A deviation from accuracy or correctness, usually from incorrect or lack of information.
• Example: Examining the wrong evidence storage device (either by being given the wrong device or picking it out yourself).? Your exam procedures may be correct, but the results are not.

Mistake (noun) /m?-?stāk/

• An action or judgment that is knowingly misguided or wrong.
• Example: Choosing to perform a forensic task without having the skill to perform it.

Suspect (noun) /?s?s-?pekt/

• A person thought to be guilty of a crime or wrongdoing, or where there is suspicion.
• Example: The custodian was seen at the workstation when the files were supposedly copied.