Practical Evidence Interpretation, Keeping It Simple

Transcription

1 Practical Evidence Interpretation, Keeping It Simple presented at: IPTM s Special Problems in Traffic Crash Reconstruction April 17-20, 2001 Jacksonville, Florida presented by: John Daily Teton County Sheriff s Department (Wyoming) & Nathan Shigemura Illinois State Police

2 Who Was Driving? A Case Study Presented by: John Daily Jackson Hole Scientific Investigations, Inc. Box 2206 Jackson, WY (307) jhsi@rmisp.com

3 Introduction Many times when investigating/reconstructing a traffic crash, a disproportionately large amount of emphasis is given to the mathematical analysis phase. However, without a proper and thorough initial investigation, where all available physical evidence is gathered and interpreted, an effective mathematical analysis is almost impossible. Additionally, many times a mathematical analysis is not crucial to the case at all. However, good old fashion investigative skills are ALWAYS crucial to every case. Remember GIGO Garbage In, Garbage Out!

4 Introduction (cont.) This presentation will examine two case studies. Good and bad investigative techniques of each case will be discussed. The impact (both actual and potential) to each case from what was or was not done in the investigation will be discussed.

5 Case Study #1 Who Was Driving?

6 Case study 1 - Introduction This case study involves a collision between a full-sized pickup and an ATV with two riders. There were two issues to be addressed: How fast was the pickup going when brakes were applied? Who was operating the ATV at the moment of collision?

7 What are we going to do? First, we will look at the scene. Next, we will look at evidence from the ATV. What evidence was NOT gathered? Thirdly, we will examine evidence from the pickup. What evidence was NOT gathered? We will examine the injuries to the ATV riders. We will use scene evidence to compute the pickup speed. How can we get the ATV speed? How do we determine who was operating the ATV?

8 What Happened? A deputy sheriff was operating a department pickup truck and was running Code 3 to back up another deputy. He was approaching a hillcrest on a gravel county road. The road curved to the right immediately after the hillcrest. The deputy saw an ATV with two riders in his lane. He dynamited the brakes and began a straight skid. The ATV operator began a right turn to re-gain the proper lane. The pickup skidded into the left side of the ATV. The collision killed the female rider on the ATV. The male rider had his left leg amputated just below the knee by the collision. The male occupant was intoxicated. Some witness statements put him as the driver. He was charged with Aggravated Vehicular Homicide.

9 Scene Examination Let s look at the scene diagram:

10 Scene Elevations

11 Important Scene Evidence Total skid length of pickup: 146 feet. Level road drag factor (mu) for THIS pickup (rear ABS): Elevations range from level to 12% downgrade for the pickup. Pickup location at brake application. Area of Impact location. Final rest of pickup. Final rest of ATV NOT available. Moved by bystanders before investigation. Radius of tire scuffs made by ATV NOT available due to inadequate measuring.

12 What was NOT gathered from the Scene or ATV riders? Clothing from female rider. Various witness statements said she was in shorts of unknown length, unknown type shirt, and white shoes. Clothing from male rider. Various witnesses had him attired in darker shoes, long blue jeans, and unknown type shirt. Evidentiary blood samples from female. Hair samples from either rider.

13 Evidence from ATV NONE of the following evidence was gathered by investigators: Blood Fat Other tissue Material transfer to engine case ATV was placed in unsecured storage

14 Blood, Fat, Tissue from ATV

15 Left side of ATV

16 Rear of ATV

17 Right side of ATV

18 Front of ATV

19 Broken Battery on ATV

20 Underside of ATV

21 Left Handlebar Damage to ATV

22 White Material Transfer to Engine Case

23 Scratching on left front side of rear carrier on ATV

24 Evidence from the Pickup The pickup was placed in semi-secure secure storage. The following evidence was NOT gathered from the pickup: Blood and tissue. Liquid splash on front bumper (probably battery acid). Fabric impressions on front bumper. Fabric impressions on hood. Black rubber-like material transferred to front bumper (probably tire material from left rear ATV tire). Hair and fiber evidence.

25 Fabric impression from left of front bumper

26 Discoloration on left side of pickup bumper most likely battery acid

27 Tire tread pattern from ATV transferred to pickup bumper

28 Blood - left front of pickup

29 Medium velocity blood spatter - left lower pickup fender

30 Blood & Tissue left corner of front bumper

31 Injuries to male ATV rider Most severe injury was crushing of the left leg just below the knee. Bones were splintered and lower left leg effectively amputated by the collision. No significant head injury. No significant thoracic injury. Numerous small lacerations and abrasions.

32 Injuries to Female ATV rider Large avulsion on left calf on outside of leg just below the knee. Most ribs on left side fractured. Fatal injury was aorta separation. No broken leg bones. No head injury. Numerous abrasions, contusions, and small lacerations.

33 What else do we know so far? Much of the evidence available was not gathered immediately. Biological and other transferred evidence was gathered six months after the collision at the direction of the reconstructionist. Initial speed estimate by investigators was based upon improper grade information and a too short skid mark measurement. This estimate was 34 mph in a 35 mph zone. Male ATV rider was charged based upon BAC and some witness statements saying he was driving. No evidence was available at this time to corroborate.

34 After forensic analysis, what do we have? Basic scene measurements and elevations. Final position of pickup. Point of brake application for pickup. Area of impact. Damage to ATV and pickup. Injuries to both riders of the ATV. Fabric impression on pickup bumper. Tire print from ATV onto pickup bumper. Shoes from both riders became available late in the investigation.

35 What are we still missing? Blood analysis whose blood is where? Tissue analysis whose tissue and what is it? Clothing of both riders cannot examine clothing for transferred pattern evidence.

36 Let s start putting it together We will address the speed issue first. What method are we able to use? COLM? Combined speed? Time Distance?

37 COLM This will NOT work in the practical sense. WHY? Momentum ratio between the two vehicles is too high. We can say a lot about the speed of the pickup at impact but not much about the speed of the ATV. Scene evidence shows us the pickup path did not deviate at collision, implying the relative collision forces were low at least with respect to the pickup.

38 COLM (cont.) There is not very much damage to the pickup, indicating a small EBS. Remember EBS and delta-v V are not usually the same! Finally, we do not know the final rest position of the ATV.

39 Combined Speed We will use a combined speed technique to determine the speed of the pickup, both at impact and brake application. Why not just a slide to stop? The grade of the road is changing throughout the skid, thus changing the effective drag factor of the road.

40 Let s look at the scene elevations again

41 Summary of Pickup Speed calculations From post-impact to final rest, using distance, grade, and mu measured, we get about 26 mph. Add 1 mph delta-v V to the pickup to account for speed change in the collision. Use combined speed from 27 mph impact speed to get 41 mph at start of braking. Range of likely speeds were 39 to 43 mph at onset of braking.

42 How do we get the ATV speed? We can use time-distance. Where can the pickup driver first see the ATV? Where is the ATV at that point in time? How far is the ATV from impact when the drivers can see and react to each other? About the only technique we have. Suggests the ATV was between 15 and 20 mph, with 15 mph being more likely.

43 WHO WAS DRIVING? Begin by taking both vehicles to the scene. Match damage / material transfer to put vehicles back together. Photo shows matching ATV tread to marks on bumper.

44 Putting the vehicles together Paint transfer from ATV rack to pickup fender and vise-versa. versa.

45 Putting the vehicles together (cont.) All damage / transfer is matched. Wheels of ATV turned to right. Enough space is left to allow placement of exemplar riders.

46 Male Driver Scenario Exemplar riders have same build and stature as those in crash. Note lower leg positions.

47 Male Driver Scenario (cont.) Fabric impression on front bumper face. Male in jeans, female in shorts.

48 Male Driver Scenario (cont.) Note bent elbow on left arm of male. No reported injury. Male lower left leg aligned with bumper corner. Female lower leg between bumper and ATV.

49 Male Driver Scenario (cont.) Note damage to pickup fender and hood in relation to male s left chest.

50 Male Driver Scenario (cont.) Left shoe worn by male driver does not match material transfer to engine case.

51 Nothing adds up for male driver! Male s lower left leg was amputated by collision. Would his leg have been trapped between the bumper and ATV if he were driving? NO! Serious (fatal!) chest injuries? Look at damage to fender and hood. NO! Shoes in proximity to engine case? YES! BUT wrong shoes! Fabric impression on bumper in line with lower leg? NO!

52 Female Driving Scenario If the male was not driving, then logic says the female had to be. Will the evidence show this? Height of avulsed injury corresponds to height of end of bumper.

53 Female Driving Scenario (cont.) Location of fabric impression on bumper face. Much closer to male lower leg than previous scenario.

54 Female Driving Scenario (cont.) Notice exposure of left female chest to impact with pickup hood and fender. Note female foot position. Fat spatter behind female left leg.

55 Female Driving Scenario (cont.) Hood and fender in proper location to strike female in left chest. Male leg in proper position to leave fabric impression on bumper. Female leg in proper position to be hit by left bumper end, causing avulsed injury without breaking any bones.

56 Female Driving Scenario (cont.) Shoe worn by female rider. Black material transferred to shoe. White material transferred to engine case. Cut in shoe in proximity of edge of recoil starter hole.

57 Female Driving Scenario (cont.) Foot and shoe position relative to the engine case.

58 Female Driving Scenario (cont.) Exemplar female reported this seating position was more comfortable for someone her size if she were on the back of the ATV. Shoe not far enough forward to show the markings it did. Nothing else lines up.

59 Everything adds up for female driver! Avulsion injury to female leg without broken bones consistent with bumper end impact. Female chest unprotected by arm, in line with hood and fender damage to pickup. No fabric impression in vicinity of bumper end. Fabric impression on bumper does line up with male leg position when female is the driver. Female shoe is proper color and in proper position to leave white material transferred to engine case. Female shoe has cut and material transfer on it consistent with engine case contact. Fat spatter on engine case and vicinity on ATV, consistent with avulsed injury on heavy female.

60 Summary We were asked to address two issues: What was the speed of the pickup? Who was driving the ATV? Simple speed analysis enables us to show the pickup was going about 41 mph at brake application, with an impact speed of about 27 mph. No magic or complicated math was required for this speed analysis. s. An investigator trained to the IPTM Advanced level could handle this problem. The evidence clearly shows the female was operating the ATV when the collision occurred, even though some evidence was unavailable. A degree in biomechanics was not required to reach this conclusion just plain detective work and a bit of knowledge of the mechanisms of injury. These are things a trained crash investigator should know.

61 Epilog The reconstructionist advised the prosecuting attorney of his findings and advised him to dismiss the charges against the male. The attorney could find nothing wrong with the logic but elected to go ahead with the trial. The reconstructionist was not called as a witness by the prosecution. He was on the witness list and was under subpoena. The defense attorney called the reconstructionist, who testified along the lines of this presentation. The male defendant was acquitted.

62 Case Study #2 To Brake or Not to Brake

63 Case study 2 - Introduction This case study involves a collision between a full- sized (40 ft., cab-over) motor coach (bus) with a passenger car and a pickup truck. The bus is a commercial motor vehicle and is equipped with air brakes. The issue to be addressed was the overall scenario of the crash. A second issue became evident as the investigation progressed.

64 What are we going to do? First, we will look at the scene. Next, we will look at evidence from the vehicles. We will explore witness statements as compared to the physical evidence. We will examine additional evidence from the bus. We will use physical evidence to reconcile discrepancies between statements made and what appears to be the crash scenario. We will determine the true scenario of the crash.

65 What Happened? A full size bus, carrying teenage church band members, was proceeding northbound on a two lane state route approaching a T intersection with a US route. At this location the state route approaches the US route (a north-south road) from the southwest and makes a sharp right curve to T with the US route. As the bus approached the sharp right curve it attempted to slow but could not. The bus veered around the inside of the curve and sideswiped the lead car in a line of four vehicles stopped at the stop sign. The impact pushed the car to the left, with the bus continuing into the intersection. The bus struck a southbound pickup truck in the passenger side, injuring the occupants, with a 4 year old being the most severely injured.

66 Scene Examination Let s look at the scene diagram: N US 67 X crash location IL 267 Woodson Road

67 Important Scene Evidence Tire marks left by the bus as it veered to the right displayed diagonal striations. Gouges and departure tire marks from the sideswiped lead car were present in the roadway. After impact with the car the bus continued to leave curved, striated tire marks in the roadway as it progressed into the intersection. The bus then struck the southbound pickup truck. Gouges and departure tire marks from the pickup truck were present in the roadway. Skidmarks from axle #2 of the bus were present in the roadway AFTER the collision and led to the final position of the bus. No pre-impact deceleration marks were present from the bus.

68 Important Witness Statements The bus driver stated that he started pushing on the brakes prior r to the crash but the brakes worked very little, [the bus] just wouldn t stop. He first noticed a problem with the brakes and stopped in a small town to have the brakes looked at (approximately 16 miles south of the crash). No repair service was available so he traveled on. o He stated that he felt that the brakes were not working properly and was planning to stop and have them adjusted at the next large city. As he tried to stop prior to the crash, he felt a stiffness in the brake pedal. Four passengers of the bus stated that they heard the bus driver stating/shouting about the brakes going out just prior to the crash.

69 Initial Brake Inspection of the Bus Recall, it was an air brake system. Showed no obvious defects. Steer axle was equipped with Type 24 brake chambers, axle #2 with Type 30, DD3 and axle #3 (a booster axle) with Type 9. The brake chamber on axle #2, right side, appeared to be new. Air system of the bus was charged from a tow truck. The pressure in the system built up to 105 lbs. and held steady. Low air warning device on the dash worked correctly. Push rod stroke length for each brake chamber was measured and found to be in compliance with federal motor carrier safety regulations.

70 So.. Based on the inspection of the brake system of the bus, the bus had more than sufficient braking capability and should have been able to stop the bus. Thus, the bus driver was lying about having no brakes RIGHT!!!??? But what about the witness statements???

71 Second Brake Inspection of the Bus The engine was successfully started and was able to idle unassisted. The air compressor functioned at idle and was able to build the air pressure in the brake system to psi at which point the cutoff actuated. The low air warning device functioned properly, activating when the pressure dropped to approximately 55 psi. The spring brakes activated when the air pressure dropped to approximately 42 psi. At full pressure the driver s foot pedal was depressed. It went completely down to the stop with little resistance.

72 Second Brake Inspection of the Bus (cont.) A tow truck was cabled to the front of the bus and dragged it while the foot pedal was depressed. All wheels turned and no effective braking was observed. Thus, since the motor carrier inspection showed that the brakes of the bus were in compliance and should have produced effective braking, and given the fact that they didn t when proper air pressure was present in the system, a further and more detailed inspection was necessary in order to find the cause of the brake problem.

73 The Bus Begin the quest for the cause of the defective brakes at the front, starting with the driver s area. Need to methodically examine the entire brake system since all wheels reacted the same, which suggests it s not a problem local to any one wheel.

74 Brake Pedal of the Bus Seen are the gas pedal and brake foot pedal of the bus (right pedal and left pedal respectively) looking from the right side. Note the rod under the brake pedal which acts as a stop for the pedal. Driver stated that the pedal was stiff perhaps against the stop???

75 Treadle Valve Seen is the treadle valve of the bus mounted on the bulkhead. The linkage which connects the treadle valve to the driver s foot pedal is seen at the top of the valve. Photo is taken from the front of the bus looking rearward and is underneath the driver s area.

76 Treadle Valve (cont.) Close up of the treadle valve mounting plate. The upper and lower left mounting bolts of the plate can be seen. Note the cracks in the plate and the missing pieces. The cracks go completely through the plate.

77 Treadle Valve (cont.) Viewing the treadle valve mounting plate. A piece of the mounting plate was easily lifted out by fingers.

78 Treadle Valve (cont.) View the right side of the treadle valve mounting plate. Seen are the right upper and lower mounting bolts and left upper mounting bolt. Note the cracks to the plate between the right upper and lower mounting bolts. Also note the severe fracture to the area below the right lower mounting bolt where the horizontal portion of the plate meets the vertical portion.

79 Effect of Treadle Valve Defect The cracked mounting plate of the treadle valve severely impacted the braking function of the bus. Each time the driver depressed the foot pedal, the linkage pushed on the treadle valve as it should. However, because the mounting plate was severely cracked the treadle valve was able to move and rock every time the linkage pushed on it.

80 Effect of Treadle Valve Defect (cont.) This, in turn, prevented the valve from fully opening to allow full air pressure to be applied. Sufficient air was reaching the brake chambers to move the push rods (making it possible to take measurements) but not enough air was being delivered to allow full brake forces to be developed. Hence, NO BRAKES!!!

81 Epilog Based only on the initial inspection, the bus appeared to have proper and functioning brakes. This would imply that the driver was lying about not having brakes. To jump to this conclusion would have been easy but would have ignored other witness statements and the physical evidence at hand. As a result, the wrong scenario would have been reported and the driver could have been wrongly charged.

82 Conclusions As crash investigators and reconstructionists, we need to keep several things in mind We are NOT advocates we are investigators, the finders of fact. We need to collect all of the evidence as soon as it is practical. We need physical evidence to corroborate witness statements. We need to understand the significance of the evidence we do collect. If we are too close to a case, we need to find another competent investigator to work it. We should always remember in criminal cases that someone s freedom depends on the accuracy and integrity of our work. We MUST do our best!