Value of paint transfer and damage examinations in the forensic investigation of boat collisions

Abstract

Key information sought in a boat collision investigation includes: path and direction of boats, speed, impact angle, impact site, and evasive actions. Boat collision and road traffic collision investigations are similar in application of dynamics, Newton's Laws and kinetic energy, and in examiningdamages, contact evidence, and navigation lights. Unlike road accidents, boat collisions do not leave skidmarks and scars on roads. Road vehicles usually follow clearly marked lanes and directions and come to rest on the ground after collision, unlike boats in open seas. The positions and orientations of boats when investigated can differ markedly from those immediately after engagement. Finding collision debris is more difficult in boat collisions— debris could sink to a murky seabed or disperse and float away from the impact site. Like road vehicles, boats may suffer full impact or partial impact collisions. A displacement hull may cause a slamming (full impact) or a sideswipe, dependingwhether impact occurredator away from the impactedboat's point of rotation. A high-speed boat with a planing hull may ramp up onto a low-profile boat, pushing it down into water. The nature and extent of damages depend on relative sizes, boat design, construction, strength of the structural framework, hard parts, and shell plating materials. 3-D movements such as rotation (yaw), pitching, and rolling are easier and more pronounced on water. Flooding due to the entry of water can critically affect buoyancy, centre of gravity and stability, and may capsize and sink the swamped boat. The analysis of damages on the gunwale, bow, deck, and hull, complemented by identification of paint transfers (chips, smears and rub-off), can reveal contacting surfaces and the directionality of the colliding vessels. Contact damage and induced damage include: holes, dents, imprints, bending, collapse, protrusions, fractures, abrasion, scrapes (scoring), and scuffmarks. Damages in the boat and injuries to occupants may indicate occupant kinematics. If undisturbed, the positions of the throttle, levers, gauges and switches, propellers and rudder provide a critical snapshot at collision. GPS equipment and voyage data recorders provide critical information, but unfortunately are usually found only on larger and more sophisticated vessels or military and law enforcement boats. Toxicological analysis indicates whether the boat operator was under influence of medication, alcohol or drugs. Eyewitness accounts must be carefully evaluated against physical evidence. Case studieswill be used to illustrate the value of damage and paint evidence in boat collision investigations.