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US: NIST working to get forensics labs to measure laser pointers for court cases

The National Institute of Standards and Technology is working with law enforcement to measure the actual power and divergence of laser pointers used against aircraft. NIST hopes to develop a Hand-Held Laser Characterization System for about $10,000 to $30,000 which can be used in FBI or police forensics labs. This will help in prosecution of cases of lasers illegally aimed at aircraft.

The effort began when NIST physicist and laser safety officer Joshua Hadler worked with the U.S. Attorney’s office on a 2013 case in Fresno, California. Hadler already had devised a relatively simple and inexpensive way to accurately measure laser pointer powers. (His widely-reported study showed that a majority of pointers exceeded the U.S. limit of 5 milliwatts.)

But power is only one factor of the potential laser hazard. The beam spread, or divergence is another key factor. This is because a wide, high-divergence beam will have its energy spread out more, making it dimmer and less hazardous at a distance than an otherwise equivalent-power laser with a narrower, low-divergence beam.

To tackle this, Hadler used a pyroelectric laser camera to measure the laser’s divergence. From the power and divergence, and knowing the approximate distance to the aircraft from the Federal Aviation Administration incident reports, Hadler was able to calculate the irradiance, or laser power over a given area.

The information helped to get a conviction in the Fresno case. Hadler noted that in the past, “...the vast majority of prosecutions were failing, due in no small part to a basic lack of knowledge about the laser devices on the part of nearly everyone in the trial process, including lawyers, judges, and jury members. What they needed was to be able to acquire and present quantitative data about a device's power and its effects at a specified range that could be used in the judicial process."

Hadler will present a paper on February 21 2014 at the American Academy of Forensic Sciences meeting in Seattle, Washington. The paper, “Output Characterization of Handheld Lasers Used in Criminal Aircraft Illumination,” will discuss the needed measurements and will present ideas for having these measurements be done outside of NIST, in law enforcement forensic labs.

From PhysOrg