Taking fingerprints in the investigation of crime cases requires accurate techniques. The slightest smudge or gap in a fingerprint can render a computer analysis yieldless, or omit the details needed to identify a suspect. If you have specific questions about this, try to seek guidance from the police or the agency you will be sending fingerprints to.
If you are taking fingerprints just to fill your spare time, try reading the article on how to take fingerprints using a pencil.
Step
Part 1 of 2: Taking Fingerprints
Step 1. Prepare the fingerprint card
You can print fingerprint cards for free from images on the internet. Try visiting this site used by the FBI and other US authorities. Place the card in a special holder or place a weight on it to keep it from sliding.
If this fingerprinting is for official purposes, you may have to use an authorized fingerprint card as well. Even if the card in the link above can be used, for official purposes, you may have to go to the appropriate authority. In the US, the guidelines found on the FBI's website can be used
Step 2. Decide how to take fingerprints
There are several ways that can be used to take fingerprints. The following are some of the most commonly used:
- Ink pads: look for special "porelon pads" for taking fingerprints. Use like a regular ink pad. You don't need to prepare anything.
- Glass plate: pour printer ink, or fingerprint ink onto a glass plate or metal plate at a certain point. Use an ink roller to even out and lighten the coating.
- Inkless pads: special pads that won't leave smudges on fingers are also available. Read the user manual to determine the necessary preparatory steps.
- Fingerprint scanner: this is an electronic device. The use of the fingerprint scanner is not described in this article. Read the user manual, and make sure it complies with the regulations of the competent authority.
Step 3. Clean hands
Ask the person to be fingerprinted to wash their hands to get rid of any dust that might interfere with the fingerprint. Check the towel for lint, and ask him to clean it if there is one. If soap and water are not available, medical alcohol is the next option.
Ask the person to sign the card before washing their hands. Use black or blue ink
Step 4. Hold her hand
The person cannot take his own fingerprints. You're the one in charge of picking it up. Grasping the base of the thumb, tuck the unused finger under your hand. Use your other hand to hold the person's finger just below the tip of the nail, and across the third knuckle.
- Keep the wrist in line with the arm. If possible, slide the fingerprinting table so that it is at arm's height.
- Ask him to look away, if he seems to want to move his hand. The resulting fingerprint will appear more clearly if you are the only one controlling the hand.
Step 5. Rotate your thumb over the ink
Try to keep the ink on the pad from the top of the thumb to about 6 mm below the first knuckle. Rotate your thumb onto the ink pad until the right and left sides are well coated. Allow the ink to stick beyond the area where the fingerprint was taken, smoothing it out until the ink touches both sides of the fingernail.
You can remember the direction from "awkward to comfortable" try turning your thumb and you'll understand what it means
Step 6. Rotate the thumb over the fingerprint card
Look for the part marked with the thumb. Rotate your thumb over the card as before. Rotate at a constant speed and at low pressure. Changing the spin rate or pressure can make fingerprint recordings blend. Rotate your finger only once, don't go back and forth.
Immediately lift your thumb when you're done so the results don't blend
Step 7. Repeat on the other finger
Make a fist so that only the back is visible, then turn your palms up. This is the "awkward to comfortable" turning direction that the finger should follow. Apart from the direction of rotation, the other fingerprinting steps are the same as the thumb. Take the fingerprint of the right hand, then continue with the thumb and other finger on the left hand.
- If you are using a plate filled with ink, you will need to redistribute the ink on it before each other fingerprint. Otherwise, the resulting fingerprints may overlap.
- Make sure to record the fingerprint in the appropriate square on the card, and the result covers the part of the finger between the two sides of the nail, and 6 mm below the first knuckle.
- Let the person being fingerprinted wipe the ink on the right hand before moving on to the left.
Step 8. Take a flat tape
In the fingerprint card there are usually two more boxes for recording the thumb, and two large boxes marked "4 fingers at the same time". Place your fingers on the ink in the same order as above (right thumb, right hand, left thumb, left hand), and press your finger onto the paper, without turning it. Record 4 fingers at once. You will often have to rotate your fingers a bit to get everything to fit in the space provided.
- These fingerprints are referred to as "flat" records.
- This recording is used to ensure that other fingerprints have been recorded in the correct box. Some parts of the fingerprint are also more clearly visible in this footage.
Part 2 of 2: Troubleshooting
Step 1. Paste the paper over the wrong fingerprint
Glue a small piece of paper to the wrong fingerprint box due to blending, only partially picking up, or some other problem. Re-record fingerprints on this paper. However, using more than two sheets of paper like this will make your fingerprint card likely to be rejected.
US law enforcement agencies can order this paper officially from the FBI
Step 2. Change the amount of ink
If the edges of the fingerprint are covered with black smudges, too much ink has been used. On the other hand, if any part of the fingerprint is white, too little ink is used. Try reducing the ink on the plate, or replacing the ink pad if you use one.
Many plain ink pads are not suitable for use in fingerprinting. So, it's best to use porcelain bearings
Step 3. Dry the sweat with a cloth or rubbing alcohol
Faint fingerprints are usually caused by sweat (or inappropriate ink). Wipe the rag to dry the sweat, and immediately take the fingerprint. Medical alcohol can also help dry hands.
Step 4. Pay attention to the missing part of the fingerprint
If there is anything that prevents you from fully recording your fingerprint, write it down on the card, or the card will be rejected. Usually the cause, is "totally amputated finger", "fingertip amputated", or "birth defect".
In the US, more than normal fingers are not recorded by the FBI. However, other authorities may require you to record the fingerprint on the back of the card. Read the specific guidelines for each use of the fingerprint card
Step 5. Solve hard-to-take fingerprints
Fingerprints on people with various professions or certain hobbies may be eroded over time. If fingerprints are difficult to capture clearly, try one or more of the following techniques:
- Press or swipe the fingerprint down from your palm to your fingertips to make it more prominent before picking it up.
- Wipe the eroded fingerprints with lotion or cream.
- Apply ice to the fingerprint, then dry it and take it. This method is very suitable for use on wrinkled fingerprints or smooth hands, not on eroded fingerprints.
- Use only a small amount of ink and press very gently.
- Make a note of the condition of the fingerprint, especially if it is completely eroded. Take note of what work is causing this problem.
Step 6. Fill in all the information in the card
The fingerprint card may be rejected if the information on it is incomplete. Use black or blue ink to fill in each square. If you are unsure about filling in the information in one box, ask a more experienced colleague, or look up the agency's guide on the internet. Even if the information on weight and date of birth must be filled in according to the applicable format to produce consistent data.
Step 7. Perform analysis on fingerprint
Understand the basics, and it will be easier for you to understand fingerprint recordings.
- About 95% of people have circular fingerprints (with curved lines like the letter U) and/or circles. The other part is an arch with a line that goes up and bends, or forms a peak, then continues to extend outwards and doesn't curve back. Be sure to get a fingerprint record that is clear enough to determine the type.
- "Delta" is the point in the fingerprint, where the lines from three different directions meet. If there is not a single point in the curve or circle of the fingerprint line, make sure that all of it has been taken. This point is rarely seen. In this case, you should write a note on the card "no delta point, ink has been applied all over between the fingernails."
Tips
- Store the poroleon pads upside down to make them last longer.
- Abnormal hand shape requires special techniques. Try rolling the ink directly onto your finger, sticking the paper to its surface, and gluing it to the fingerprint card. Make a note of the abnormal finger condition in the space provided.
