The core or cores of a fingerprint are defined for all pattern types except for plain arches. Core-like patterns can also appear in palmprints, lower joints, or plantar impressions, and should be marked using the same guidelines as fingerprint cores. When they are present, cores appear in highly curved areas of a ridge impression and are identified by the innermost recurving ridge, sometimes called the innermost recurve. A recurving ridge curves back on itself, making an elongated horseshoe shape; the innermost recurving ridge is the one that does not surround any other recurving ridges. If you imagine the most curved part of the innermost recurving ridge as a circle segment, the core location is the center of that circle.

When an innermost recurving ridge is present on a tented arch, the core is defined and can be marked. Plain or central pocket loop whorls will have only one core if the innermost recurving ridge is circular, or two cores if the ridge is elliptical. The table below details the possible numbers of cores for each ridge pattern type. EFS differs from the Science of Fingerprints (SoF) in its specification of location for cores: the EFS location of cores for loops is at the focus of the innermost recurving ridge, rather than on the ridge itself. Unlike the NCIC method, EFS also defines core locations for whorls and some tented arches using the focus of a recurving ridge. The EFS core locations were developed based on input from AFIS vendors and SWGFAST, specifically because these locations are not as sensitive to the presence or absence of appendages, and are therefore more reliably detected by automated systems.

Pattern Classification		Cores	Deltas
Arches	Plain arch	0	0
	Tented arch	0 or 1	0 or 1
Whorls	Plain whorl	1 or 2	2
	Central pocket loop	1 or 2	2
	Double Loop	2	2
	Accidental whorl	Any Number	Any Number
Loops		1	1

If one or more cores are present and the feature set is from a fingerprint, the Pattern classification/PAT should be defined. This does not mean that the classification has to be known definitively, but it must at least exclude plain arches. For plain arches, a Center point of reference/CPR may be marked instead of marking a core.

The core's direction moves along the ridge flow at the core, pointing away from the innermost recurving ridge. If the core is the center of a complete circle made by a whorl pattern, its direction is not defined. If the direction of ridge flow is not clear at the core, a range of direction uncertainty can be used to include the range of possible directions of ridge flow.

When marking the location of a core, you may also indicate a radius of uncertainty. If it's relatively clear where the core is, this radius should be small. If the image is unclear or ambiguous, make the radius of uncertainty large enough to include all possible locations of the core.

In the special case that the core cannot be seen in the impression but you can make a reasonable estimate of its location, you may if desired mark the core in the approximate location. Include an appropriately large radius of uncertainty.

Find the most curved section of an innermost recurving ridge and visualize the circle it is a part of. Identify the circle's center point and click to mark the core location, then drag along the ridge flow for the core's direction direction. Click a second time to indicate a radius of uncertainty: the distance you click from the core's center point will be the radius.

If the print has a second core, mark it in the same way. Use the erase tool to remove any mistakes, then click Check My Answer.