  Currently, many Wi-Fi access points are being installed in urban areas. This
paper considers how this infrastructure can be used to assist criminal
investigations and improve public safety. We propose a criminal investigation
assistance system that uses multiple wireless local area network (LAN) access
points and cameras. The proposed "Criminal Fishing System" enumerates candidate
media access control (MAC) addresses of culprits' mobile devices from probe
request signals gathered by access points during the period in which a culprit
is near the scene of an incident. Preliminary experiments demonstrated that the
proposed system could identify the MAC address of the culprit's device, which
would allow authorities to capture the culprit's radiowave fingerprint. After
enumerating the candidate MAC addresses, the culprit's usual appearance can be
obtained by surveilling these MAC addresses, especially when it changes less
frequently. Moreover, the MAC address itself can be admissible as evidence that
the culprit was near the scene of an incident, given that the MAC address is
static, that is, it has not changed after the incident, or the original MAC
address can be retrieved from the randomized MAC address.
