Is Laser Technology (LIDAR Device) a Reliable and Acceptable Method to Measure the Speed of a Motor Vehicle
In Goldstein v. State, 339 Md. 563, 664 A.2d 375 (1995), the trial court heard evidence to determine "the reliability and acceptance of the LTI 20-20 [LIDAR device] in the particular scientific community." Goldstein, 339 Md. at 565, 664 A.2d at 376.
The prosecution and the defense each called its own scientific expert to testify.
The prosecution's witness was an astrophysicist who was "well-versed in the use of lasers to measure distances and speed." Goldstein, 339 Md. at 576, 664 A.2d at 381.
According to his testimony, the LTI 20-20 was "generally accepted as reliable and capable of measuring the speed of a motor vehicle accurately within one mile per hour." Goldstein, 339 Md. at 565, 664 A.2d at 376. the defendant's expert "worked for a maker of radar detectors and became acquainted with the LTI 20-20 in the process of developing a device for detecting laser beams as well as radar beams." Goldstein, 339 Md. at 576, 664 A.2d at 381.
He testified that "the LTI 20-20 is not generally accepted, due primarily to flaws in the particular device." Goldstein, 339 Md. at 565-66, 664 A.2d at 376.
Both experts concurred, however, that "in theory laser technology could be used to measure the speed of a motor vehicle." Goldstein, 339 Md. at 566, 664 A.2d at 376.
The trial court ruled in the prosecution's favor and the Court of Appeals of Maryland affirmed.
The Goldstein court observed that "the theory underlying the LTI 20-20 would be familiar to any student of high school physics." Goldstein, 339 Md. at 571, 664 A.2d at 379.
The court explained that laser speed devices operate on the same principle as military radar, which determines distance and changes in distance over time (i.e., speed) by transmitting pulses of microwaves and "measur[ing] the time it takes for a pulse to reach the target and for its echo to return." Goldstein, 339 Md. at 571-72, 664 A.2d at 379, citing 1 J. Strong, McCormick on Evidence 204, at 880 n.17 (4th ed. 1992).
The court noted that "laser speed measurements work exactly the same way, except that the device relies on lasers rather than microwave radiation." Goldstein, 339 Md. at 572, 664 A.2d at 379.