NCJ Number
65920
Journal
FBI Law Enforcement Bulletin Volume: 49 Issue: 3 Dated: (MARCH 1980) Pages: 11-15
Date Published
1980
Length
5 pages
Annotation
SPEEDOMETER AND TACHOMETER INVESTIGATIONS TO HELP DETERMINE VEHICLE SPEED AT IMPACT ARE DESCRIBED AND SUGGESTIONS FOR REMOVING AND HANDLING SUCH EQUIPMENT ARE GIVEN.
Abstract
BECAUSE SKID MARKS ARE NOT ALWAYS LEFT AT THE SCENE AND BECAUSE DAMAGE ESTIMATES DEPEND MORE ON GUESS THAN ON OBJECTIVE CACULATION, BOTH KINDS OF INVESTIGATIONS ARE LIMITED. VEHICLE SPEED AT IMPACT CAN SOMETIMES BE DETERMINED BY EXAMINING THE SPEEDOMETER, TACHOMETER, AND TACHOGRAPH. HOWEVER, A DIRECT SPEEDOMETER READING OF A STUCK NEEDLE AFTER AN ACCIDENT MAY NOT BE RELIABLE, PARTICULARLY IF THE READING IS AT OR NEAR ZERO. IN SEVERE HEAD-ON OR FIXED-OBJECT COLLISIONS, THE SPEEDOMETER NEEDLE MAY MAKE A VISIBLE STAMP OR MARK ON THE DIAL. AT OTHER TIMES, THE DRIVER'S BODY OR OTHER OBJECTS MAY COME IN CONTACT WITH THE SPEEDOMETER DURING COLLISION, BENDING THE NEEDLE AND CAUSING IT TO PUSH AGAINST THE DIAL. IF THE NEEDLE STICKS AND THE DAMAGE IS RELATIVELY STRAIGHT FROM FRONT TO REAR, THE VEHICLE IMPACT SPEED MAY BE DETERMINED, AND SUBSTANTIATED BY DAMAGE AND OTHER EVIDENCE. OTHER SPEED DETERMINATORS INCLUDE PAINT SMEARS ON THE DIAL LEFT BY THE NEEDLE AT THE TIME OF IMPACT AND TACHOGRPAH AND TACHOMETER FINDINGS. SPEEDOMETERS SHOULD BE PHOTOGRAPHED BEFORE REMOVAL, HANDLED GENTLY, AND REMOVED WITH THE COMPLETE INSTRUMENT PANEL, IF POSSIBLE. AN EXAMINATION REQUEST SHOULD ACCOMPANY THE SPEEDOMETER TO THE LAB, ALONG WITH A BRIEF ACCOUNT OF THE ACCIDENT, ANY SPEED CALCULATIONS, AND OTHER PERTINENT DATA. THE LABORATORY EXAMINATION CONSISTS OF OBSERVATION, MICROSCOPIAL ANALYSIS, AND PHOTOMICROGRAPHY UNDER NORMAL LIGHTING CONDITIONS AND ULTRAVIOLET (UV) LIGHT. IN SOME CASES, IT IS MORE DIFFICULT TO TAKE A PHOTOGRAPH OF VERY SMALL PARTICLES UNDER UV LIGHT THAN IT IS TO OBSERVE THEM. PHOTOGRAPHS ARE INCLUDED. (AOP)