I’m finding it very common in the mystery books I read that a character can tell a lock has been picked by tell-tale scratches on the lock. I see it enough that it’s annoying. Now, I’ve seen locks scratched to hell from keys, and I’ve picked locks, and I’ll be damned if I can tell what scratches are supposed to exist that will tell a lock’s been picked. Is this simply a writer’s trope? Lockpickers and investigators chime in!
Only if you’re a cat.
Sorry. Yes, it can leave scratches, but so can fumbling around with a key.
It might leave tiny abrasions on your tongue. Otherwise, I have no idea.
The few times that I’ve played around with picking locks, I don’t recall leaving any marks or gouges on the outer part of the cylinder. I’m sure a foresics person with some type of very small boroscope might be able to see something inside. The only way I could see leave any marks at all would be if whatever you’re using to put torque/tension on the cylinder is slipping off, and you’re holding it in so hard it’s scratching. But, as you sort of alluded to, if the metal is so soft that a few second of doing that leaves marks, 10 years of hitting it with keys will leave plenty of marks as well.
So, yeah, I’m sure picking a lock may leave some marks, but I’m less sure that any beat cop will be able to notice it than I’m that it’s just a plot device that you need to accept…unless you want to dedicate a few pages/minutes/a scene to them calling a locksmith in.
It’s fiction. 
Am I that only one that was sad to find that the thread title has a typo?
Lock picks don’t have to leave scratches. Picking the lock itself works the inside of the lock just like a key so nothing would be seen on the outside. There are destructive means of opening locks that leave obvious signs, like a broken lock. Padlocks can be unlocked with a sleeve on the hasp that might leave a scratch, but not necessarily since they’re often made from the soft aluminum from a soda or beer can. Latches can be picked and that might leave scratches on the door, jamb, or latch plate. But that’s mostly done with a credit card or similar device on a single action latch.
Oh, FFS… :smack:
Correction request sent.
I object!!!
Indeed. I was running through the scenarios in my head…
“I have a feeling I’m being stalked, and I suspect that my stalker has been licking my door locks. Is there any way for me to determine if that is the case based on the scratch patterns…?”
Or, alternatively…
“So, recently I began to stalk somebody, and I was wondering…”
Yeah, I HAD to click on this one, just because WHAT??
Moderator Note
While licking was certainly a more interesting title, I fixed the typo: licking -> picking.
To see if there were scratches the lock would have to be taken apart and the pins examined. But a key with sharp edges would also leave scratches.
My practice locks might have a few scratches on them only from my inept fumbling.
As **Joey P **and TriPolar have indicated, lock picking shouldn’t result in scratching up the outside of the lock as the lock-picking action is inside the lock, not on the face. And anyone who is going to leave scratches all over the outside is either very nervous and rushed (not a surprise) or has never picked a lock before.
The three most popular methods of turning the cylinder would be bumping, raking, and single-pin-picking. Bumping uses a sawtooth key with rapping from a light mallet to quickly jostle pins up and down—it is very effective but very noisy and probably wouldn’t be used if someone is trying to be sneaky. Raking is most likely what a locksmith would use: apply torsion to the cylinder and use one of many wiggly shaped “rakes” to massage the pins into position. Finally, the true James Bond picking is single-pin-picking, or SPP, where each pin is gently nudged, feeling for defects in the construction that give a hint at where the shear line is.
(ETA: Note that there are also nondestructive methods to get into a lock that don’t involve picking the pins, known as “bypasses,” such as the shimming attack TriPolar mentioned using soda can aluminum…)
Raking can be somewhat vigorous, and it is possible that the rake might slip out and scratch up the lock, but not likely.
Single-pin-picking is like surgery, and about as delicate.
Take a look at YouTube videos by bosnianbill to see a real professional in action. People send in locks and he picks them on camera, then guts them so you can see what was inside. Pretty cool.
Could a forensic tech could match scratches on the lock with those made by a diamond tongue stud? Maybe I should try and sell that plot point to Law & Order: SVU for the crime of the week.
Speaking as a Certified Master Locksmith…
Yes, attempting to pick a lock does leave tell-tale scratches which can be seen under magnification. I learned this in a Forensic Locksmithing class and saw the scratches myself. What you can’t say with certainty is whether the attempt succeeded or how long ago the scratches go there.
Yes, you have to disassemble the lock. No, the scratches left by a key don’t look the same.
Scenario #1: There’s a burglary, no signs of forced entry. Examining the lock reveals no tell-tale scratches. Conclusion: The lock was not picked. That leaves several options, such as 1) the intruder had a key, 2) the lock was accidentally left unlocked, 3) the break-in was staged and there is no intruder, 4) some other thing I haven’t thought of yet.
Scenario #2: There’s a burglary, no signs of forced entry. Examining the lock DOES reveal tell-tale scratches. Conclusion: Some time in the recent past, someone stuck lock picks into this lock, possibly in an attempt to pick the lock, possibly successfully. But that still leaves several options, such as: 1) the intruder picked the lock. 2) someone else tried to pick the lock three days ago and failed, then a different intruder obtained a key 3) the lock was break-in was staged and there no intruder but the resident stuck lock picks into the lock to make it look more real, or 4) some other thing I haven’t thought of yet.
Like any other piece of forensic evidence, it’s just one piece of the puzzle. Suppose you find a fingerprint at the crime scene. You don’t know when it got there. You can’t even say with 100% certainty that there aren’t two people whose left pinky fingerprints are identical. But put it together with other evidence and you can eliminate reasonable doubt.
P.S. There’s an entire organization for Forensic Locksmiths. It’s called IAIL, the International Association of Investigative Locksmiths. The president is Tom DeMont.
The shows where they actually show real lock-picking (or good phoney stuff) matches what Minor says - single-pin plus a second piece to turn the cylinder so that the picked pins each stay when moved to the right location. I assume the scratching might be made on the adjacent pins as you manipulate each pin at a time up with a metal tool. Since actual keys tend to be sawtooth, they would not leave scratches high up on adjacent pins. They would move the pins mostly from the bottom.
Can you have a lock where one pin has to go all the way up and the adjacent one all the way down? Would the key actually slide properly?
Wow. Thanks!
You can’t tell if they succeeded, but it could tell you how long ago ?
the metal will oxiidise and replace the oxide layer ? bright metal marks on the oxide layer will themselves oxidise and disappear. all of that could be measured to indicating timing.
Most keys are a flavor of softish brass. Most pins are a flavor of harder brass, or brass-plated steel. Most picking tools are steel with or without chrome plating.
Different materials leave different kinds of marks on other materials. Harder lock pins will scratch and wear down softer keys more than vice versa. Harder picking tools will scratch softer pins more than vice versa.
Ref **Isilder **just above I’m going to bet the oxidation rate on small scratches in a brass plating will be pretty slow. such that fresh or old scratches will look pretty similar.