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Evidence tracking

Evidence tracking description/claims

This application claims priority from U.S. application No. 60/700,886 filed Jul. 19, 2005, and from U.S. application No. 60/806,748 filed Jul. 7, 2006, each of which is incorporated herein by reference for all purposes.

It is not easy to keep track of evidence in a crime scene investigation. It is necessary for each piece of evidence to maintain a “chain of custody” so that the authenticity of a piece of evidence at trial can be known. At many crime scenes it is also necessary to maintain a log of the personnel entering and leaving the crime scene. The procedures required to maintain the chain of custody and the crime scene log are detail-oriented and if errors are made it can be a big problem later.

It has been proposed to use RFID tags, for example, to try to keep track of evidence and to assist in logging entry and exit of personnel from areas. Most RFID tag designs are not very workable for these purposes, as they are little more than high-tech bar codes that can only be read by a reader such as a handheld “gun” that is placed into close physical proximity with a tag to read the tag. At most crime scenes it is unworkable to try to use close-proximity readers, whether bar-code or RFID. One cannot, for example, count on a person who is entering or exiting a crime scene to do so at a location where such a close-proximity reader is located. Through inadvertence or otherwise, an evidence bag might enter or exit a crime scene boundary at any point along the boundary.

It would be very desirable if a system and method could be devised that would facilitate RF tracking of salient events at a crime scene, that would detect entry and exit at all points along a boundary, and that would more or less continually keep track of who is in the crime scene.

A system uses a large loop antenna, connected with a transceiver operating below 1 MHz. The loop antenna is deployed from a spool to surround a crime scene, and may carry indicia communicating that it is a crime scene boundary. The system interrogates devices, including evidence bags and badged personnel, as they enter and leave the scene. The system can optionally log the time of salient events. A second loop antenna can log evidence bags as they enter a vehicle. The devices can be silenced by the transceiver and thus collisions can be reduced and avoided among responses from devices. The system performs “area reads” that would not be possible if higher RF frequencies were employed.

FIG. 1 shows a typical deployment of the system according to the invention.

Turning to FIG. 1, what is shown is a typical deployment of the system according to the invention. A truck or other motor vehicle 16 arrives at a crime scene defined by corpse 15. A spool 13 is removed from the truck and is placed at a position that lies on a desired crime scene boundary. An electrically conductive line 12 is unspooled from the spool 13 and is laid out along the surface of the ground along the desired crime scene boundary, returning to the start to define a complete boundary. The line is connected to a transceiver 14 about which more will be said later. The transceiver 14 is optionally equipped with a GPRS, Edge, EVDO, WiFi, or other WAN interface permitting reporting of events to distant equipment omitted for clarity in FIG. 1.

Personnel 18 wears a badge 19, containing a radio tag. The radio tags employed can, for example, be tags such as those described in U.S. Pat. No. 7,049,963 entitled “Networked RF tag for tracking freight” and assigned to the same assignee as the present invention, which patent is incorporated herein by reference.

The transceiver 14 can, for example, be a transceiver such as that described in copending U.S. application No. 60/806,520, filed Jul. 3, 2006 and assigned to the same assignee as the present invention, which application is incorporated herein by reference. The transceiver can transmit at, say, a predetermined multiple of 32768 Hertz (the standard watch crystal frequency) such as 65 kHz or 133 kHz. The transceiver may have switchable antenna terminals to handle as many as four distinct antennae. The transceiver can switch from one antenna to the next, and even if one antenna is not well coupled with a particular tag, very likely one of the other two antennas will turn out to be well coupled with that particular tag.

The typical steps of deployment, as mentioned above, call for a line at least twenty feet in length. Each tag, whether on an evidence bag or on a badge, has a respective identifier and is disposed to receive queries at a radio frequency no greater than 1 MHz and to emit responses thereto at a radio frequency no greater than 1 MHz. In the case of an evidence bag, there is a tag mechanically affixed to the bag. The bag has an opening and a closure for the opening.

• Provisional Patent
• Utility Patent

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