Why does someone have to roll each finger while being fingerprinted?

Question

At work I sometimes get called on to help fingerprint job applicants. We have one of those LiveScan machines so there is no ink involved. My question is: Why does each finger have to be rolled over? The fingerprint is already obtained once during the initial slap of the four fingers and thumb. Does rolling make the fingerprint easier for the FBI and State Police's computer to read since it is rolled out over a larger area?

Answer 1

If you look at your own prints, you will see most have an area where the pattern meets, and forms a triangle. This is called the delta. There are also different classifications, such as an arch, loop, and whorl.

In order to classify the print, they use these characteristics as reference points. They use the center of the print, and the delta. Some prints have two deltas. Every print is different, including the location of these reference points, so the finger must be rolled nail to nail.

Answer 2

The FBI states that all fingers must be rolled for them to be entered into there files. Reasoning being the finger print / Id locater will not except hlaf finger prints. A full finger print must be from the far left to the far right. If the print is completed correctly, the print will look somewhat square. If not, FBI will refuse the print and send it back to the agency form which it was sent stating  " Not Exceptable " reprint ! Now if the subject is not in jail and has already been released, how do you reprint ? You can't, this why it's very important to do it right the first time.

Answer 3

The intitial ink slap prints are used briefly by the ident staff to confirm the identity of someone who has already been in custody at that agency.

The Livescan machine is used to send fingerprints to the BCA and the FBI to check for identity statewide and nationwide.

The fingers are rolled because the print on your finger is not just on the pad of the fingertip, but the sides as well.  Remember "Men in Black" when Smith put his hands on that machine that ereased his prints?  Well, things like that can happen, and any remnants of the fingerrprints, such as the side of the fingertips, can be used for ID if enough points match up.

Answer 4

Once the fingerprints are taken and labeled, forensic scientists use a classification system to identify them. The three basic fingerprint patterns are Whorl, Arch, and Loop. There are more complex classification systems that further break down the pattern to plain arches or tented arches. Loops may be radial or ulnar. Whorls also have smaller classifications.

Facts:

The patterns of ridges on our finger pads are unique: no two individuals—even identical twins—have fingerprints that are exactly alike.

We leave impressions—or prints—of these patterns on everything we touch with any pressure.

The prints can be visible, as when our fingers are dirty or oily, or they can be latent, as when they are made only by the sweat that is always present on our finger ridges.

Injuries such as burns or scrapes will not change the ridge structure: when new skin grows in, the same pattern will come back.

Dactyloscopy is the practice of using fingerprints to identify someone.