A 3-D STABILITY ANALYSIS OF LEE HARVEY OSWALD ?· A 3-D Stability Analysis of Lee Harvey Oswald ...…

Download A 3-D STABILITY ANALYSIS OF LEE HARVEY OSWALD ?· A 3-D Stability Analysis of Lee Harvey Oswald ...…

Post on 14-Aug-2018

212 views

Category:

Documents

0 download

Embed Size (px)

TRANSCRIPT

<ul><li><p>A 3-D Stability Analysis of Lee Harvey Oswald ... JDFSL V10N3</p><p>A 3-D STABILITY ANALYSIS OF LEE HARVEY</p><p>OSWALD IN THE BACKYARD PHOTOSrivamshi Pittala, Emily Whiting, Hany Farid</p><p>Department of Computer ScienceDartmouth College</p><p>{Srivamshi.Pittala.GR, Emily.JW.Whiting, Hany.Farid}@dartmouth.edu</p><p>ABSTRACT</p><p>Fifty years have passed since the assassination of U.S. President Kennedy. Despite the long passageof time, it is still argued that the famous backyard photo of Oswald, holding the same type of rifleused to assassinate the President, is a fake. These claims include, among others, that Oswalds posein the photo is physically implausible. We describe a detailed 3-D stability analysis to determineif this claim is warranted.</p><p>Keywords: Digital Forensics</p><p>1. INTRODUCTION</p><p>Shortly after President John F. Kennedys as-sassination on November 22nd, 1963, Lee Har-vey Oswald was arrested and charged with thecrime. Because Oswald was killed before histrial, we never heard from Oswald a full ac-counting of the details of the assassination.With so many unanswered questions of thatfateful day it is not surprising that numeroustheories have been proposed to fill in the miss-ing gaps. It has long been argued, for example,that Oswald did not act alone, but rather waspart of a larger criminal conspiracy involving avariety of government, international, or crimi-nal groups. These theories point to purportedinconsistencies in the events of November 22ndand in the evidence collected against Oswald.One such example is a photograph1 of Oswaldin his backyard (States, 1964) holstering a pis-tol and holding a rifle in one hand and Marxistnewspapers in the other, Figure 1(a).</p><p>This photo was particularly damning becauseit showed Oswald holding the same type of rifle</p><p>1Although there are three backyard photos, taken inseeming succession, we focus our analysis on only one ofthe backyard photos.</p><p>that was used to assassinate President Kennedy.At the time of his arrest, Oswald claimed thatthis photo was fake. In addition, it has longbeen argued that the lighting and shadows inthe photo are physically implausible, that Os-walds facial features are inconsistent with otherphotos of him, that the size of the rifle is incon-sistent with the known length of that type ofrifle, and that Oswalds pose is physically im-plausible (it appears as if he is standing off bal-ance). The Warren Commission (States, 1964)and the House Select Committee on Assassina-tions (States, 1979) investigated claims of phototampering and concluded that they were un-warranted. More recent studies have also re-futed the claim that the lighting and shadows inthe photo are inconsistent (Farid, 2009a, 2010).This earlier work, however, did not address theclaims that Oswalds pose is physically implau-sible. We describe the construction of a phys-ically plausible 3-D model of Oswald that in-cludes an anatomically-based mass distribution.This model allows to determine if Oswalds poseis physically plausible.</p><p>c 2015 ADFSL Page 87</p><p>This work is licensed under a Creative Commons Attribution 4.0 International License.</p><p>http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/</p></li><li><p>JDFSL V10N3 A 3-D Stability Analysis of Lee Harvey Oswald ...</p><p>2. RELATED WORK</p><p>The past decade has seen the development ofmany different and complementary approachesto analyzing a photo for evidence of manipu-lation (Farid, 2009b; Rocha, Scheirer, Boult,&amp; Goldenstein, 2011). These techniques oper-ate on the assumption that manipulation willdisrupt some statistical, geometric, or physicalproperty in an image. Manipulation is exposedby quantifying and detecting these perturba-tions. For example, format-specific analyses ex-ploit artifacts that are introduced when a JPEGimage is compressed multiple times (A. Popescu&amp; Farid, 2005; Mahdian &amp; Saic, 2009; Kee,Johnson, &amp; Farid, 2011). Pixel-based analysesdetect low-level correlations that are introducedby cloning (Fridrich, Soukal, &amp; Lukas, 2003;Pan &amp; Lyu, 2010), re-sizing (A. C. Popescu&amp; Farid, 2005a), or non-linear filtering (Lin,Wang, Tang, &amp; Shum, 2005). Sensor-basedanalyses can detect inconsistencies in chromaticaberrations (Johnson &amp; Farid, 2006), color fil-ter array interpolation (A. C. Popescu &amp; Farid,2005b; Kirchner, 2010), or sensor noise (Chen,Fridrich, Goljan, &amp; Lukas, 2008; Fridrich, 2009).And, physically-based analyses can detect in-consistencies in reflections (OBrien &amp; Farid,2012), lighting (Johnson &amp; Farid, 2005, 2007;Kee &amp; Farid, 2010a; de Carvalho, Riess, An-gelopoulou, Pedrini, &amp; de Rezende Rocha,2013), or shadows (Zhang, Cao, Zhang, Zhu,&amp; Wang, 2009; Kee, OBrien, &amp; Farid, 2013).</p><p>Physically-based methods are attractive be-cause they are applicable in low quality andlow resolution images. Within these physically-based techniques, those that can analyze 3-D scene properties are particularly attractivesince they offer a richer source of informationthan 2-D image-based techniques. 3-D stabil-ity analysis, for example, is a fundamental op-eration in engineering (Hibbeler, 2010). Be-yond design of mechanical systems, the notionof static balance has seen broad use in com-puter graphics and machine vision for anal-ysis of 3-D geometry and scene understand-ing. Static equilibrium constraints have beenincorporated into optimization techniques for</p><p>objectives such as believability of characterposes (Shi et al., 2007) and balance of 3-D-printed prototypes (Prevost, Whiting, Lefeb-vre, &amp; Sorkine-Hornung, 2013). Interactive de-sign applications apply static balance to ar-chitectural structures (Whiting, Ochsendorf,&amp; Durand, 2009; Vouga, Hobinger, Wallner,&amp; Pottmann, 2012), structurally-sound furni-ture (Umetani, Igarashi, &amp; Mitra, 2012), orsketch-based input (Derouet-Jourdan, Bertails-Descoubes, &amp; Thollot, 2010). In the realm of3-D scene analysis, static equilibrium has beenused as a prior in digital reconstruction, for ex-ample, to generate physically plausible urbanscenes from images (Gupta, Efros, &amp; Hebert,2010), reconstruct missing information in pointcloud data (Shao et al., 2014), or infer orienta-tion of man-made objects (Fu, Cohen-Or, Dror,&amp; Sheffer, 2008).</p><p>Leveraging this earlier work in 3-D stabilityanalysis, we describe a new physically-based 3-D forensic analyses for analyzing the 3-D sta-bility of a person or object from a single imageand apply this analysis to the famous Oswaldbackyard photo. Digital 3-D models such asthat used here have been widely used in var-ious applications from aerospace, automotive,defense and military systems, medical systems,and product design (Duffy, 2008). Unlike life-like mannequins, digital models offer more flex-ibility in adjusting the location, pose, height,proportions, and weight of the model. In ad-dition, a digital reconstruction allows for moreflexibility in adjusting the location and type oflight source, as well as the type of camera.</p><p>3. 3-D MODEL</p><p>We begin by fitting an anatomically plausi-ble 3-D model to Oswald in the backyardphoto shown in Figure 1(a). We start witha 3-D articulated human body of a genericmale (www.makehuman.org) of the same height(1.75m) as Oswald (States, 1964). The 3-Dmodel of the body used for our analysis has twocomponents: skeleton and skin. The skeleton isan armature representing major bones found inthe human body (spine, hands, arms, legs, feet,</p><p>Page 88 c 2015 ADFSL</p><p>This work is licensed under a Creative Commons Attribution 4.0 International License.</p><p>http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/</p></li><li><p>A 3-D Stability Analysis of Lee Harvey Oswald ... JDFSL V10N3</p><p>(a)</p><p>(b)</p><p>Figure 1: Shown are (a) the Oswald backyardphoto and (b) a rendering of our 3-D model.</p><p>etc.) The bones are connected to each other byjoints and have a rotational degree of freedomabout the joint. The skin is a textured meshof triangles that overlays the skeleton. A sim-ple colored Lambertian material is used for theskin. Although a generic 3-D head would havesufficed for our stability analysis, we employeda custom-built 3-D model generated from pho-tographs of Oswald (Farid, 2009a).</p><p>The 3-D model can be realistically posedby simply rotating each body part about itsjoint. This manipulation respects the underly-ing physiological constraints of the human body(e.g., knees are hinge joints and an arm or legcannot be made longer or shorter). This ma-nipulation was performed in Blender, a freelyavailable 3-D rendering engine. When movinga particular body part, the skin was deformedwith the armature using the built in skinningtool in Blender, which applies parenting con-straints to bones. The articulated model withskeleton (yellow) and skin (black) is shown in aneutral pose in Figure 3(a).</p><p>This articulated model was placed on aground plane with the feet making direct con-tact with the ground. A virtual camera wascreated that matched the camera used to pho-tograph Oswald an Imperial 620 Duo Lenscamera with 35mm focal length and 36mm sen-sor size (States, 1964). We manually adjustedthe position and pose of the models head, torso,arms, and legs to match Oswalds appearancein Figure 1. In the final configuration shownin Figure 1(b), the camera is 3.4m from the 3-D model and 1m above the ground plane. Thematched pose is shown in Figure 3(b). Becauseof the inherent ambiguity in constructing a 3-Dmodel from a single 2-D image, there are a num-ber of 3-D geometries that are consistent withthe 2-D image. The 3-D model constructed hereand the subsequent analysis show that there ex-ists a consistent and plausible 3-D scene geom-etry.</p><p>Because we are interested in analyzing the 3-D stability of Oswalds pose, it is necessary toadd anatomically plausible masses to the skele-ton. We used an anatomically-based model ofhuman body mass distribution (DeLeva, 1996).</p><p>c 2015 ADFSL Page 89</p><p>This work is licensed under a Creative Commons Attribution 4.0 International License.</p><p>http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/</p></li><li><p>JDFSL V10N3 A 3-D Stability Analysis of Lee Harvey Oswald ...</p><p>This mass distribution model divides the hu-man body into disjoint segments and assigns aportion of the total mass to each segment. Thebody segments and their corresponding share ofthe total body mass are: head (6.94%), trunk(43.46%), upper-arms (22.71%), forearms (21.62%), hands (20.61%), thighs (214.16%),shins (2 4.33%), and feet (2 1.37%).</p><p>We treat each segment of the body as a pointmass located at its respective center of mass.This is a discrete representation for the gravi-tational force on each segment, where weight isapplied as a single resultant force vector. Bypositioning a point mass at the center of mass,the discrete force vector applies a net force andnet torque that is equivalent to the continuouscase (Hibbeler, 2010). The point mass for eachsegment is assigned its share of the total mass 2</p><p>of Oswald (64.4 kg) (States, 1964). The lo-cation of the center of mass for each segmentwas determined by a body mass distributionmodel (DeLeva, 1996) in which the center ofmass was placed along the length of each bone.These positions for each body part are shown inFigure 2 and Figure 3(c).</p><p>In the last step, we added a 3-D model ofthe rifle and pistol since the masses of thesemay affect Oswalds overall stability. The War-ren Commission identified Oswalds rifle as a6.5mm Mannlicher-Carcano, measuring 1.02min length and 3.4kg in weight (States, 1964).A 3-D model of a generic rifle was scaled tothe same length and its center of mass wasplaced halfway along its length. Oswalds pis-tol, a Smith &amp; Wesson 0.38 caliber revolver, is20.0cm 14.0cm 4.0cm in size and has amass of 1.0kg. A 3-D model of a generic pis-tol was scaled to the same size and its center ofmass was placed at the models center of mass,thus assuming a uniform density material. The</p><p>2The Warren Commission report states that at thetime of his arrest, Owald gave his weight as 63.5 kg(140 lbs) but on other occassions he gave weights of both63.5 kg and 68 kg (150 lbs). The New Orleans policerecords of his arrest show a weight of 61.7 kg (136 lbs),and the autopsy report indicates an estimated weight of68 kg. Given the conflicting weights, we assume a weightof 64.4 kg (142 lbs) the average of the various reportedweights.</p><p>posed model with masses and rifle and pistol isshown in Figure 3(d).</p><p>One way to validate our 3-D model is to alignthe rendering of the 3-D model with the origi-nal backyard photo. The alignment, Figure 4,shows a good agreement between our model andthe photo. A second way to validate our 3-Dmodel is to verify that the shadows cast by ourmodel match the shadows in the original photo.To this end, we model the sunlight as a dis-tant point light source and manually positionedthe light until the shadows in our model bestmatched the photograph. As can be seen inFigure 4 the cast shadow on the ground planeclosely matches the original photo. And, shownin the lower panels of Figure 4 is a magnifiedview of Oswalds head showing good agreementof the shadows under the nose, lip, and neck(see also (Farid, 2009a, 2010)).</p><p>We conclude that we have constructedan anatomically plausible and consistent 3-Dmodel of Oswald in his backyard. This 3-Dmodel adds more evidence contradicting theclaims that the shadow and lighting and lengthof the rifle are physically implausible.</p><p>4. 3-D STABILITYANALYSIS</p><p>The stability of a 3-D model is determined bycomparing the projection (along the directionof gravity) of the models global center of massto its base of support. If the projected centerof mass is contained within the base of support,then the 3-D model is stable (Goswami, 1999).</p><p>The center of mass ~c for our 3-D model of Os-wald is computed from a weighted sum of bodysegments, the rifle, and the gun:</p><p>~c =</p><p>(14i=1mi~ci</p><p>)+ mp~cp + mr~cr(14</p><p>i=1mi</p><p>)+ mp + mr</p><p>, (1)</p><p>where mi and ~ci, i [1, 14], correspond to themass and center of mass of each body segment,and mp,~cp and mr,~cr, correspond to the massand center of mass of the pistol and rifle, re-spectively. Each mass is a scalar value and eachcenter of mass is a 3-D point. The overall 3-D</p><p>Page 90 c 2015 ADFSL</p><p>This work is licensed under a Creative Commons Attribution 4.0 International License.</p><p>http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/</p></li><li><p>A 3-D Stability Analysis of Lee Harvey Oswald ... JDFSL V10N3</p><p>(a) (b)</p><p>(c) (d)</p><p>(e) (f)</p><p>Figure 2: The relative location of the center of mass for each body segment (yellow dot).</p><p>c 2015 ADFSL Page 91</p><p>This work is licensed under a Creative Commons Attribution 4.0 International License.</p><p>http://creativecommons.org/licenses/by/4.0/http://creativecommons.org/licenses/by/4.0/</p></li><li><p>JDFSL V10N3 A 3-D Stability Analysis of Lee Harvey Oswald ...</p><p>(a) (b)</p><p>(c) (d)</p><p>Figure 3: The 3-D articulated skeleton in a neutral pose (a), adjusted to match Oswalds pose (b),with the addition of masses (red dots) (c), and with the addition of a 3-D model of the rifle andpistol (d).</p><p>Page 92 c 2015 ADFSL</p><p>This work is licensed under a Creative Commons Attribution 4.0 International...</p></li></ul>

Recommended

View more >