Federal Investigations · Agency Guide

ATF Investigation Defense Attorney

Deandra M. Grant
Reviewed by Deandra M. Grant, JD, GC, MS, ACS-CHAL Forensic Lawyer-Scientist
Updated July 29, 2026
Read time 8 min
The Short Answer

The ATF investigates firearms, explosives, and arson offenses — straw purchases, falsified Form 4473s, unlicensed dealing, National Firearms Act violations, and machine gun conversion devices. For licensed dealers, a criminal case frequently begins as a routine compliance inspection.

ATF cases divide into two kinds. One begins with an undercover purchase or a trace on a recovered gun. The other begins with an inspector reviewing a licensee's records.

Both can end in a federal indictment, and the second catches people who thought they were dealing with an administrative matter.

What the ATF investigates

Prohibited person possession under § 922(g), firearms in furtherance of other crimes, straw purchases, false statements on federal firearms forms, unlicensed dealing, trafficking, National Firearms Act violations, explosives offenses, and arson.

eTrace and NIBIN

When a firearm is recovered at a crime scene it is traced through eTrace from manufacturer to distributor to the first retail purchaser. If that purchaser is not the person who had the gun, the question becomes how it travelled — and a straw purchase theory follows.

NIBIN links cartridge casings across incidents ballistically, which is how a single recovered firearm becomes evidence in several cases at once. Both systems produce leads rather than conclusions, and the inferential step from trace to culpability is where the defense works.

Straw purchases and the Form 4473

Buying a firearm from a dealer requires completing ATF Form 4473, which asks whether you are the actual transferee or buyer. Answering yes while buying for someone else is a false statement offense under § 922(a)(6) and § 924(a), and it is charged frequently.

The contested element is knowledge and intent at the moment of purchase. Buying a firearm as a genuine gift is lawful and the form accommodates it. Someone who bought for themselves and later sold or lent the gun did not make a false statement when they signed. The government's proof is usually circumstantial — who chose the gun, whose money paid, how quickly it changed hands — and each of those is contestable.

NFA violations and conversion devices

Unregistered short-barrelled rifles and shotguns, suppressors, and machine guns are National Firearms Act offenses. The category producing the most prosecutions now is the auto sear or "switch" — a small device converting a semi-automatic pistol to automatic fire.

The exposure is severe and often misunderstood. Possession is an NFA offense in itself, and if the firearm is connected to a drug offense, a § 924(c) count carries a 30-year mandatory minimum for a machine gun. Defendants who bought a novelty part online routinely have no idea of that exposure.

When a compliance inspection becomes criminal

Licensed dealers are subject to ATF inspection of records and inventory. Most findings are administrative — recordkeeping violations, missing 4473s, inventory discrepancies. But a pattern of missing forms, sales to prohibited persons, or off-book transfers can be referred for criminal prosecution as wilful violations.

The dividing line is wilfulness, and the moment an inspection starts producing questions about intent rather than paperwork, it has changed character. That is the point to stop explaining and get counsel — statements made to an inspector are available to prosecutors.

Undercover operations

ATF runs undercover purchases, and in the private-sale and unlicensed-dealing context the volume and pattern of transactions is the whole case. Whether someone was "engaged in the business" of dealing versus selling from a personal collection is a genuine question, and the statutory definition has been amended in recent years — which makes the timing of the conduct relevant.

What to do if agents contact you

Do not answer questions. Say that you want to speak with a lawyer, and say nothing else. That is lawful, it cannot be used as evidence of guilt, and it is the single most effective thing you can do. Lying to a federal agent is a separate felony under 18 U.S.C. § 1001 — no oath required.

Do not consent to a search. If agents have a warrant they do not need permission. If they are asking, they may not have one.

Do not destroy anything. A preservation duty attaches the moment you know of the investigation, and destroying records is its own felony.

Write down what happened. Names, badge numbers, agency, time, what was asked, what was taken. Do it the same day.

Then call (214) 225-7117. If an agency is already at your door, the investigation is well advanced — and the pre-indictment window is the most valuable period you have.

Key Terms

The words that come up most on this page, in plain English.

Form 4473
The federal firearms transaction record completed at purchase. A false answer supports a criminal charge.
eTrace
ATF's system for tracing a recovered firearm from manufacturer to first retail purchaser.
NIBIN
The ballistic network linking cartridge casings across incidents.
Auto sear
A device converting a semi-automatic firearm to automatic fire. Treated as a machine gun.
Engaged in the business
The statutory threshold above which firearm sales require a federal license.

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Deandra M. Grant
Written & Reviewed By

Deandra M. Grant, JD, GC, MS, ACS-CHAL Forensic Lawyer-Scientist

She holds a Master of Science in Pharmaceutical Science and a Graduate Certificate in Forensic Toxicology, both from the University of Florida. She is the author of The Texas DWI Manual and has defended Texas DWI cases since 1994.

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