Lockpicking Forensics - RSS 2.0 Feed
Lockpicking Forensics - ATOM 1.0 Feed


Destructive Entry

Destructive entry (or forced entry) is a non-covert method of entry characterized by damage to or destruction of a lock, safe, or surrounding objects, such as a door, window, or wall. It is by far the most common method of entry and is frequently used by law enforcement and military personnel for rapid entry to a residence or facility. As you might have guessed, there are many ways to destroy things. Techniques are classified by their method of destruction in terms of the physics of the operation but often overlap and complement one another. All destructive techniques use energy or force to damage, displace, weaken, or destroy components. Once components of a lock, safe, door, window, or wall lose structural or molecular integrity their ability to resist compromise is considerably reduced. The general categories of destructive entry are: chemicals, compression, impact, shearing, temperature, tension, and torsion.

While the techniques discussed might seem advanced, the majority are rather simple when put in perspective; doors are kicked in, padlock shackles are cut, locks are drilled, et cetera. Techniques are categorized to help the investigator identify, define, and study new attacks. While tool designs differ greatly the tool marks and forensic evidence they leave behind may help investigators quickly identify the techniques used to gain entry.

Destructive Entry Principles

Chemicals are used to affect the molecular structure of components. Chemicals, namely acids, can corrode, disintegrate, or dissolve components. Like temperature, chemicals often leave components vulnerable to other attacks.

Compression is the use of pressure against a component in complementary directions. Essentially, the opposite of tension. It causes distortion, compaction, or breakage of components. Compression is most often used to reduce the strength of materials so that other methods can be used.

Impact is the use of pressure and shock against a component. Striking and explosives are most common. Impact has a wide variety of results including fracturing, breakage, deformation, and compression. Some methods of bypass use impact to retract the locking bolt, most of which are destructive. Explosives are one of the most dangerous methods of destructive entry and use has dwindled with time as safer alternatives, such as drilling, have become popular.

Shearing is the use of pressure on a component placed betweeeen two edges. Cutting, chopping, and drilling are included in this category. Drilling is the most popular method of destructive safecracking and removal of locks by a locksmith. In general, drilling is probably the easiest, fastest method of destructive entry.

Extreme temperature can be used to affect the molecular structure of components. High temperatures can vaporize, burn, melt, or re-temper components. Re-tempering can leave components soft or brittle, thus vulnerable to many other attacks. Low temperatures are less common, but can be used for similar purposes.

Tension is the use of pressure on a component in opposite directions. Stretching, pulling, prying, bending, or ripping are included in this category.

Torsion is the use of rotational pressure (torque) on a component. Twisting and torque and included in this category. Causes shearing, compression, and deformation of components.

Destructive entry is fairly straightforward in terms of method of entry, so the focus is on tool mark identification. The forensic locksmith must be wary of destructive techniques used as a method of hiding covert or surreptitious entry. A thorough investigation will reveal covert techniques and can potentially rule out destructive entry as the method of entry due to improbable direction, angle, or position of tool marks.

Forensic Evidence

The most common attack against padlocks is cutting the shackle, either in half or clean off. Almost all low to medium security non-shrouded padlocks are susceptible to this attack. This attack is a form of shearing, and the two edges of the bolt cutter are clearly seen in the displacement of the shackle material.

A bolt cutter was used to shear the shackle of this padlock in half.

A closer examination of the tool mark reveals that a red substance is present in the area where the bolt cutter was used. This could be a variety of things; paint, dirt, grease, or rust. We might be able to match this material to the tool if a bolt cutter is found in a suspect's possessions.

A dark red material is found when the tool mark is examined closer. Possibly paint or rust from the bolt cutter.
A KIK cylinder that has been drilled at the shear line to allow the plug to rotate freely.

Drilling, a form of shearing, is the most common method of destructive entry against all types of locks. It is frequently used by locksmiths to remove locks when they cannot be opened non-destructively. In this photo, the plug of a KIK cylinder has been drilled at the shear line, allowing the plug to freely rotate.

The plug is taped to prevent materials or residue from being lost during removal or transportation.

On the Forensic Investigation page we discuss the need to tape any openings in locks recovered at the crimescene. In the photo, a large amount of metal is present inside the lock, a product of drilling. This material is preserved because it may contain evidence useful to the investigation, such as shards of a broken drill bit.

Striae from the drill bit can be used to link a specific drill bit to the scene of the crime.

Drills are much like firearms in terms of forensic evidence. Bullets fired from a gun have striae based on the barrel used; the same goes for drill bits used in destructive entry. In the photo, the spiral striae left by the drill bit can clearly be seen in the plug of the lock.

Impact is a versatile method of destructive entry that is extremely effective against windows, doors, and walls. In the photo, a padlock has been hammered until the shackle broke. The direction of the break can tell us what angle it was being struck from. Additional tool marks will likely be found on the body of the padlock.

A padlock was repeatedly struck with a hammer until the shackle broke.

In this photo, the body of the padlock shows tool marks in places where the hammer impacted the lock. The crescent shaped marks are numerous and can be measured to determine the size and shape of the hammer used. At least three different points of impact are visible.

Tool marks from the hammer used during this entry can be found on the body of the padlock.
Heavy damage to the front of the lock and the keyway profile caused by a screwdriver or chisel type tool.

Heavy damage to the face or keyway of the lock can mean many things. A thorough investigation of tool marks, including angles and positions, helps to reveal how entry was accomplished. In this photo the keyway has been considerably widened and gouged so a tool can be inserted, probably a screwdriver or chisel.

The upper pin chamber itself has been sheared off rather than the individual pins.

In addition to damage to the keyway, the upper pin chambers have been completely sheared off, leaving the plug and broken cylinder free to rotate in the lock. This attack appears to be torsion applied counter-clockwise to the plug through the use of a screwdriver.

The pins inside the lock show heavy damage cause by a screwdriver or chisel being hammered into the plug.

The pins inside this lock show heavy damage from where the screwdriver or chisel was forced into the keyway. Examination of what is left of the tip of the pin shows no indication of covert entry techniques. Because of the force used, tool marks on the pins are rather distinct and may later be used to link suspects to the crime.

European profile cylinders are held in place by a screw that extends through the center of the cylinder. Because the cam is beneath this point, it is the thinnest part of the lock and thus the easiest to break. In this photo, a european profile cylinder has been snapped in half (forced to the left) using common hand tools.

A euro-profile cylinder that has been broken at the central weak point, near the set screw.

The basis of this attack is that there is enough of the cylinder extending through the door, as little as a few millimeters, and a tool used to grab and apply force to the lock. In this photo, tool marks can be seen where the tool was used to grab the front of the lock.

Tool marks found on the front of the european profile lock identify that it was gripped with a tool.

The cam of the lock can also be examined to determine which way the lock was snapped. This is generally not important, but the lock may have been snapped at an angle that is impossible when the door is closed, indicating fraud or misdirection from the real method of entry.

The crushed cam of the lock helps identify which direction the lock was snapped in.
The shackle of a padlock that has broken at two separate points.

Many destructive attacks against low security padlocks break the shackle because, relative to the body, it is the weakest component. In this photo, the padlock shackle is broken in two places, with one piece being stuck beneath the locking bolt.

The side of the padlock shows signs of unnatural distortion and twisting.

A thorough examination of both the shackle and the padlock body helps to identify the specific technique used. In this photo, the body of the padlock shows excessive distortion in the form of twisting, indicative of extreme torsion being applied to the padlock body.

Tool marks found on the edge of the padlock body appear to be fresh and indicate torsion as the technique used.

Tool marks for the torsion tool are found on the edges of the padlock. Marks appear to be rather fresh, thus the most likely candidates for the attack in question.

Closer inspection of the tool mark shows a series of parallel striations consistent with a wrench.

A closer inspection of the tool mark shows a series of parallel teeth marks, probably from the use of a plumber's wrench or tongue-and-groove pliers. Marks can be used in tool mark comparisons done with tools found in a suspect's posessions.

Simulating lockpicking is common in insurance fraud or when the insurance holder is worried about coverage. These people rarely understand lockpicking and just jam a screwdriver in the lock to make marks. In most cases, material removal and tool marks are present at the front of the cylinder but not past the first or second pin.

Simulated lockpicking usually uses a screwdriver to gouge the keyway leaving large and plentiful tool marks.

The pins in simulated lockpicking will have a large amount of material removal and tool marks that are not consistent with any type of covert entry, including lockpicking or key bumping. Marks will usually not be found on the pins in the back of the lock, too.

Tool marks found from simulated lockpicking are not consistent with normal lockpicking nor key bumping.
Use of chemicals to distort the molecular structure of components has varied effects.

Chemicals are powerful because they can fundamentally alter metals to leave them vulnerable to many other attacks. In this case, brass pins are dark red/brown because of NO2 fumes released when concentrated nitric acid contacted the brass components. Nitric acid has the effect of eating away the copper in brass.


A closer examination can confirm the use of nitric acid by identifying trace evidence left by the chemical reaction between nitric acid and brass. The scattered blue particles are cupric nitrate and zinc nitrate, a byproduct of the chemical reaction.

If you would like to help this site by donating any destructive entry tools or locks that have been compromised via destructive techniques, please contact me.