What is a “physically-locked room”? In short, it refers to cases that happened in a room that is truly locked. Such rooms could be described as: no secret doors or gates, with doors and windows locked from inside and keys placed inside.

So, it leaves two roads for the criminal to take:

  • Enter the room and commit the crime, then locked the room from the outside. In this case, tricks to lock the room are the keypoint.
  • Commit the crime without entering the room. On this occasion, the criminal must consider how to commit the murder and dispose of the weapon

In this chapter, we will dig into the previous one, that is, “tricks to lock the room“.

(Note: In the beginning article, I have supposed the criminal to be a single person.

Locking doors seems to be of no difficulty, but in practice, it sets several limits to the criminal: 

  • Above all, using spares keys or passkeys is forbidden (for it would make things too easy), which urges the criminal to make use of available items to accomplish the goal.
  • Next, the job must be down as quickly and quietly as possible, otherwise, he may be witnessed by an unfortunate person passing by. So, tricks like dismantling the door and assembling it back might need well consideration.
  • Finally, as our detectives and readers are pretty smart, the criminal had better leave no trace after using his items.

However, the desire for commiting murder is greater than anything. No matter how many the limits are, and more and more sealed the rooms become, criminals still come up with various ways to break into them. And that is truly admirable (except from the fact that detectives are still the final winner). So below, I’ll introduce some most popular tricks, just for a start-off.

1. The murderer attachs strong thread (like fishing lines or strings) to the bolt or the key, then drags it outside through the door gap or the ventilation opening. Now, if he pulls the thread with proper force and angle, the direction of the force changes, and will then encourage the movement of the bolt or the key, which helps lock the door. Also, if the knot has been tied properly, it would easily be restored by making a sharp pull. This type of trick, although requires some technique, has high adaptability. (See Picture 1)

Picture 1

2. The murderer normally closes the door with the key, then uses a “bridge” to send it back inside. For example, the murderer first fixs a needle to the furniture, then inserts long thread to the pinhole and drag it to the outside through the ventilation opening. Now, if he straightens the thread, a “ropeway” consisted of double thread will be created, and the key can easily slide its way back to the room. Finally, pull the thread sharply and make the needle fall off, only leaving a tiny pinhole on the furniture. (See Picture 2)

Picture 2

3. The murderer uses long sticks to move the bolt or the key through the ventilation opening or the burglar proof window and makes the door locked. Such tricks are very easy to perform, but require for a wide gap and a proper angle.

4. The murderer takes advantage of the vibration, produced by slamming the door, to shake the bolt down in order to lock the door. As you may tell, this type of trick somewhat relies on randomness, but might have a surprising result on some occasions.

5. The murderer uses a certain item to support the bolt, and carefully close the door. Then, if he managed to get rid of the item, the bolt would automatically move due to gravity, thus lock the door. A typical case would be the use of ice–easy to get, and bearly leave any trace. Another idea is, just like Method 4 shows, using vibration to shake the item down.

6. The murderer inserts the key into the keyhole, then uses two long, thin metal strips to clamp the key through the keyhole from the outside. Now, as long as he rotates the strips, the key would then follow the movement and lock the door. Of course, this requires some technique. There’s another idea: using strong magnet to attract the key, thus making it rotate.

I would say, that the focus of the previous section is mainly on murderers’ side. So what about detectives’ side? How would  detectives find the evidence? Maybe we’d better answer this accordingly:

1. In order to change the direction of the force, certain items might be used as turning points along the way the thread goes. And, at these turning points, due to friction, the thread will leave scrapes on them. So, one of the keys would be finding scrapes.

2. Now that needles were used, pinholes must have been left where needles were fixed. Search around the place the key was found, and you may find out the truth.

3. Well, the trick itself would leave little evidence, so maybe you should judge from the structure of the room. For example, suppose there was a room, with window close to the door, and protected by merely burglar proof bars, then you know what kind of trick would be used.

But, think again, isn’t Method 1 appliable too in this case? (And more technical, if you persue such thing.)

4. In this case, you may focus on the lock itself. Is the bolt some kind of too flexible? Will it move because of vibration? Try it, and you will find out.

5. Now we need to consider two situations. If the supporting item is ice or something that disappears by itself, then you may try to find the trace it leaves–damp, in the case of ice. For the other situation, think about: is there anything that is of proper size but not supposed to be in this room? If there is, it might just be what the murderer has used.

6. This is pretty easy. Was the key in the keyhole when the door was broken into? If so, then you should be careful.

As I have mentioned, these tricks are far from being complicated. If you want true challenges, then go and look for the works of the petantry school” (衒学趣味 in Japanese). But, if you ask me, I would say, all those complicated start from the basic.

Well, the first part of physically-locked rooms is over, thanks for reading! Do you like it or not? Please, feel free to leave a comment!

To be continued.


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