To take fingerprints and investigate a crime, it is necessary to use some very precise techniques. A smudge or empty space can frustrate computer work and analysis or alter the details needed to locate suspects. If you want to know how to take a fingerprint, read this article.
If you want to take them for fun, use a pencil and a piece of duct tape.
Steps
Part 1 of 2: Taking Fingerprints
Step 1. Prepare the fingerprint card
You can download it by searching through the free images online and print it. Try the one used by the FBI and other US agencies. Place it on a special stand or secure it with a heavy object so it won't slip.
If you want to take fingerprints for professional purposes, you should find a card in the format that complies with the rules for taking fingerprints
Step 2. Decide which method to use
There are several methods for taking fingerprints. Here are some of the most common:
- Ink Pad: Get a "Porelon" pad for fingerprints. Use it like a regular ink pad. No preparation is needed.
- Glass plate: on a glass or metal plate, previously fixed in one place, put a small amount of printing ink or fingerprint ink. Roll it out with a rubber ink roller until it is thin and even.
- Ink-free impression sheets: there are special pads that do not stain your fingers. Read the product instructions, because in some cases special preparation is required.
- Fingerprint scanner: it is an electronic device. The process is not considered in this article. Read the product instructions and make sure it complies with the rules for taking impressions.
Step 3. Clean your hands
Ask the affected person to wash and dry their hands to remove any dirt that could affect fingerprints. Check that no towel residue sticks to your fingers and ask her to remove it if there is one. In the absence of soap and water, denatured alcohol is the best alternative.
Have her sign the fingerprint sheet before she washes her hands. Use a pen with blue or black ink
Step 4. Grab the person's hand
You don't have to fill in the fingerprint card yourself. The person in charge of carrying out the sampling must perform this task. Take her thumb, keeping the other fingers under your hand. With the other, place your thumb on the swab and press it from the underside of the nail to the last phalanx.
- Keep your wrist level with your hand. If you can, move everything you need to take impressions to his arm level.
- Ask the subject to look away if they appear to be cooperating. The prints will be clearer if you control the hand.
Step 5. Run your right thumb over the ink
Your goal is to soak the thumb from the nail 6mm below the last joint with ink. Place the side of the thumb closest to the index finger on the ink, pressing on the nail. Make your entire fingertip rotate on the pad and continue until it reaches the opposite side of the nail.
You can remember the direction by keeping in mind that you have to start from the most uncomfortable position to get to the most comfortable one. Try the movement to understand it better
Step 6. Press your thumb on the fingerprint card
Find the area marked for the right thumb. Rotate your ink-soaked finger on the card, in the same direction as before. The movement must be uniform accompanied by light pressure. If you change the speed or pressure during this operation, smudging may occur. Rotate your finger only once, avoiding moving it back and forth.
When finished, lift your thumb to avoid smudging
Step 7. Repeat the same operation with the other fingers
Join your hands with the back facing the ceiling, then turn them bringing the palm up. This is the direction in which they have to rotate the fingers - the same direction from the most uncomfortable position to the most comfortable one. Apart from this change, the procedure is the same as that of the thumb. Take the fingerprints of the right hand, then the left thumb, then the fingers of the left.
- If you use a glass or metal plate for picking, you need to apply more ink each time you take a new fingerprint, otherwise you may get an image consisting of two overlapping fingerprints.
- Make sure that each fingerprint is placed in the right box, that it is taken from one side of the nail to the other and 6mm below the last joint.
- Ask the subject to clean their right hand before moving on to the left.
Step 8. Take fingerprints at the same time
The card should contain two boxes for the thumbs and two larger spaces for the four fingers to be imprinted at the same time. Following the order indicated above (right thumb, right hand, left thumb, left hand), dip your fingers in the ink and press them on the card without rotating them. As for the four fingers, you have to imprint them at the same time, rotating them slightly so that they all fit into the space provided.
- These fingerprints are also called "flat" fingerprints.
- They are used to verify that each footprint is in the correct box. In addition, they highlight features that may not be visible on complete ones.
Part 2 of 2: Correcting the Errors
Step 1. Correct errors using labels
In case of smudges, partial fingerprints and other inaccuracies, you can mask the problem by gluing a small square of sticky paper on the board. Take the fingerprint again and imprint it on the label. However, if the card contains more than two, it may be invalidated.
The investigating authorities can cancel the cards they deem unsuitable
Step 2. Change the ink quantity
If the edges of the print aren't sharp, you have used too much ink. If, on the other hand, white areas appear, it means that you have used little. If you are using a pickup plate, try again by imprinting more or less ink. If you use a tampon, you probably want to replace it.
Many general purpose swabs are not suitable for taking fingerprints. Get a "Porelon" swab
Step 3. Wipe away sweat with alcohol or a washcloth
Generally, if the fingerprints are not very clear and defined, the cause is sweat (or an inappropriate type of ink). Clean your finger with a cloth and take the impression immediately. Denatured alcohol also allows you to wipe sweat off your hand.
Step 4. Write a note when the withdrawal cannot be done correctly
If there is a reason why you are unable to take the fingerprints in full, write it down, otherwise the card will be rejected. The prints may be partial or absent due to the amputation of a finger or hand, but also due to a congenital malformation.
Extra fingers are not registered by the FBI. Other authorities may request registration on the back of the card. Follow the instructions provided by the competent bodies for taking impressions
Step 5. Manage the toughest fingerprints
It is possible that fingerprints will alter over the years due to work or a hobby. If they're not noticeable, try one of these techniques:
- Before sampling, prepare your fingertips by pressing or rubbing them in a downward motion from the palm of your hand to your fingers.
- Rub your worn out fingertips with a hand lotion or cream.
- Hold some ice against your fingertip, then dry it and take the impression. This method is most effective when the hands are soft and the pads of the fingertips are not very pronounced, but not if they are rather damaged.
- It uses little ink and applies very gentle pressure.
- Note the condition of the footprints, especially if they are extremely smooth. Add the cause of this alteration.
Step 6. Fill out the entire form
It could be rejected if there is missing information. Use a blue or black pen to fill in each box. If you are not sure what to write, ask someone who has more experience or follow the instructions provided by the competent bodies for taking impressions. You must also provide the exact information in the "weight" or "date of birth" boxes so that they conform to the database.
Step 7. Scan your fingerprints.
By familiarizing yourself with the main notions, you will be able to notice any anomalies. Here are the first rudiments:
- 95% of fingerprints form scrolls (or U-shaped ridges) and / or spirals (circles). The others form arches, with crests that give rise to a curve or a point, and then continue forward instead of curving again. Make sure the footprint is clear enough to determine which type it belongs to.
- The "delta" is a point where a ridge is formed from three different directions. If you don't see one in a scroll or spiral, make sure you have taken the impression correctly. It is rare that a delta does not appear, but in this case you should note on the card that it was not, despite the fact that the imprint was taken from one side of the nail to the other.
Advice
- In case of hand malformations, special techniques must be used. Try applying the ink directly to your fingertips, wrapping pieces of paper on your fingers and stamping them on the card. Write down the anomaly in the space provided.
- If you use "Porelon" pad, keep it to last longer.
