Page 198 - Automated Fingerprint Identification Systems (AFIS)

STANDARDS AND INTEROPERABILITY 183

print examiners make 50 identifications on 40 unique individuals. Consider also
that each of these latent prints were searched an average of two times on the
AFIS system. What is the hit rate? The following factors have to be included to
answer this question:

1. How many unique cases were entered?
2. How many latent searches were launched?
3. How many idents were made as a result of these searches?
4. How are multiple idents on a single case counted?
5. Is the hit rate calculated by the number of unique cases, multiple searches
of the same case, or all latents received?
6. Are data management system reports used to calculate a hit rate?
7. If so, how are test/demos controlled?

8.5.3.1 How Many Unique Cases Were Entered?
In this example, there are 80 crime scenes and 80 cases. Any statistic using cases
has to refer to 80 cases.

8.5.3.2 How Many Latent Searches Were Launched?
Personnel collected 100 latent prints from these 80 crime scenes. Each print
was searched on the AFIS system an average of two times. Some searches pro-
duced an ident after the first search; others may have been searched two or
more times before being entered into the unsolved latent file. There are 200
searches for these 100 latent prints.

8.5.3.3 How Many Idents Were Made as a Result of These Searches?
There are 50 latent prints that are identified from 40 unique individuals. Forty
individuals were identified from 50 latent prints.

8.5.3.4 How Are Multiple Idents on a Single Case Counted?
If a crime scene produces two or more latent prints, and both of these prints
are associated with the same individual, for reporting purposes is this consid-
ered one ident or two? For example, if two latent prints considered to be of
value are found, searched on the AFIS system, and found to be the number 2
and 3 fingers of the same person, how should this be counted?
Consider the same case, but with eight latent prints, five of which are ulti-
mately linked to three individuals. Are there five idents or three idents? Five
idents (the number of latent prints identified on the AFIS system) divided by
the number of latent prints collected (eight latent prints) yield a hit rate of
5/8, or 63%. Three idents (the number of individuals) divided by the number
of latent prints collected (eight latent prints) yields a hit rate of 3/8, or 37%.
Five or three idents made in one case; case closed at 100%.