Approximately 2000 cases of illegal use of explosives take place every year in the U.S. Many of these are probably not preventable. However it is now possible to detect explosives in particular situations or scenarios where importance or vulnerability are high. Some of the possible characteristics or signatures of explosives that might make them more detectable are reviewed--particularly vapors and compositions. An example is given of the transport of explosive vapors through baggage to show the magnitude of the detectables and the uncertainties involved. A number of technologies that have been applied and some that are under investigation are presented. Progress has been made in increasing the sensitivity of instruments to detect some commercial explosives. The plasma chromatograph is technically the most promising device for routine explosive vapor detection because of its potential high sensitivity, specificity and ability to sense for a number of explosive vapors simultaneously.
The Aerospace Corporation under contract to the Law Enforcement Assistance Administration (LEAA) is supporting the development of a novel explosives-vapor detector based upon photoacoustic spectroscopy. This paper reviews the principles and history of the method. The encouraging progress to date, obtained through subcontracted programs that characterized explosives vapors and environmental species and that measured photoacoustic absorption coefficients of selected explosives vapors and pollutants, is briefly described
A system of tagging explosives with inorganic phosphors to yield post detonation information is described with particular emphasis given to the optical instrumentation involved. The taggant consists of small cemented aggregates containing a "spotting" phosphor plus magnetic material for recovering the taggant, and various combinations of rare-earth "coding" phosphors which contain coded source information which, because of record keeping, can identify in many cases the last legal purchaser of the explosives. By employing various fluorescent colors for the "spotting" phosphor the taggant may also be used to quickly identify the type of explosive used ("permissible" or non-permissible) during routine inspections by mine inspectors. The design of two portable high-powered 254 nm ultra-violet lamps used in locating the taggants by their "spotting" fluorescence is described, including a unit that has been certified as "permissible" for use in methane-air mixtures such as may be encountered in an underground mine. The information contained in the "coding" fluorescence is extracted by exciting the tags with the 325 nm output of a cadmium laser and measuring the resulting rare-earth fluorescence spectrum. This spectrum may be obtained in times ranging from a few milliseconds to a few minutes depending on the optical instrumentation chosen. The two methods that have been used to date for recording the fluorescent "coding" spectrum are by a scanning grating monochromator and by a multi-channel optical analyzer. These systems are descirbed as well as a proposed system using an acousto-optic filter to sample the spectrum at programmed wavelengths.
A portable radiographic unit consisting of an x-ray generator and two solid state image converter units is being used for counter-intelligence and criminology purposes in West Germany. The unit eliminates the need for making hundreds of radiographs of suspect objects.
Forensic scientists have been, for several years, seeking a rapid, sensitive and relatively inexpensive analytical method for the quantitative determination of trace elements in gunshot residues. The "Paraffin Test" was introduced in 1935 and used for many years to identify deposits of nitrate and nitrites associated with gunshot residues. However, in recent years, the reliability of this technique has been questioned. Neutron activation has been applied to the determination of barium and antimony in gunshot residues. This technique has adequate sensitivity but has not gained widespread acceptance because of the expense and time required to complete the analysis.
In this paper a variety of currently fabricated image intensifiers are discussed. The operation of these tubes is explained and their main characteristics distinguishing them from other types are described. The most important characteristics for the performance are noise characteristics expressed by the signal to noise ratio at the output S/No and imaging characteristics expressed by the Modulation Transfer Function (MTF). Current efforts concentrate on improving these two parameters and on lowering fabrication costs.
In the early seventies, dark spots were noticed on image intensifier tubes which had been used to observe detonations. This paper deals with the research and development resulting in an improved flash-proof image intensifier tube which is fully interchangeable with unprotected image intensifier tubes. Intensification, contrast transfer, and operational life of flash-proof tubes are similar to unprotected tubes. All sizes of image intensifier tubes can now be manufactured with a flash-proof feature.
Many fields of photographic applications have a specific need for a compact, intensified camera for taking pictures of moving objects under low light level conditions. In obtaining the required camera characteristics there are several trade-offs to be considered. This design is based on maximum camera gain and minimum camera size and weight with electrical gating. The system is capable of hand-held operation at 1/3 full moon. A prototype which has been constructed and is currently undergoing field evaluation is described.
What proved to be a vital development for the Army in its efforts to seek out and destroy the enemy now proves just as effective for the United States Customs Service. The problem for the Army was battling enemies familiar with the terrain--thus having the tactical advantage--under cover of night. The solution was night vision systems, which shifted the advantage to the Army. Night is the prime time for drug smuggling by land, air and sea. To increase night-time effectiveness, the law enforcement community and Customs, in particular, are relying more and more heavily on night vision technology.
A need exists for a versatile, compact, automatic system that will covertly record vehicle license plates. They cannot be successfully recorded by straight infrared photography. Alternative highly red sensitive recorders of all types reduce the apparent subject contrast below the identification level. An alternate approach making use of a texture enhancing light system is described. The method has been placed in service and has consistently produced covert records of both high and low apparent contrast license plates on vehicles crossing the U.S. border. The design approach used is detailed and the complete system is described.
In the nineteen thirties, before the great Government crime laboratories were established, individual scientific workers in the Federal agencies were sometimes called upon to settle important questions that the detectives could not handle. For this purpose, it was often necessary to invent new techniques to tackle problems by new approaches. The laboratory man needed to develop imaginative ways of looking at fragmentary material that became available. This presentation will deal with three episodes involving original procedures. The procedures proved their point in the issues at hand, but the findings were never used in court so far as the author is aware. They have not been published or publicly disclosed. If a board has been sawed into three pieces of which the middle one is missing, how do you establish that the end pieces were once joined? If a method of recognizing typescript is developed that provides quick and convincing evidence of identity, what are the chances that a sophisticated forger, knowing the technique of recognition, could successfully imitate the identity? What do you do if the exhibits in a murder case are effective and relevant evidence so far as the facts are concerned, but indicate that another and critical piece of evidence is missing? Suppose that without the missing piece, nothing else has firm meaning! These three examples are chosen for presentation because, although the microscopical techniques that were used are interesting, they appear to have lain dormant for over forty years.
Obtaining a recognizable image of a person is the most common objective of the law enforcement officer using surveillance photography. What the officer needs are some simple guides for choosing the correct equipment. It is the objective of this paper to present a few of the important guides, namely those for choosing a camera, lens, film and shutter speed. It is hoped that after applying the guides, the surveillance photographs obtained will help solve today's law enforcement challenges.
We survey the variety of three-dimensional imaging methods now available including stereo photography, integral photography, holography, laser stereometry, and moire photography. We then survey the applications of those methods in law enforcement offering a guide as to which methods are best for which application.
Current practice in many law enforcement agencies finds photography uninspired in both principle, prestige, and practice. Habitually the newest recruit on the force inherits the photographic detail. Just about the time he becomes somewhat proficient in this field a new recruit appears and takes over the photographic tasks, so that picture making never makes a really progressive step. By using a standard approach to the more important tasks, those of scenes of crime, even the relatively untrained can do the necessary on crime scene problems with reasonable assurance that the results will support prosecution labors. The Standard For Crime Scene Photography comes from an international body of forensic photographers patterned after the British Qualifying Associations. EPIC offers an Associateship and a Fellowship to workers meeting its standards.
A photographic handbook called The Photographers Guide presents a systematic and quantitative method for selecting camera systems and their conditions of use. Its purpose is to ensure that the required level of object space resolution is successfully recorded. It features a unique nomagraph which relates: resolution in object space, object distance, lens focal length and image plane resolution. Typical field performance data is given for 35mm SLR camera systems. Other data tables cover effects such as handheld cameras at slow shutter speeds, motion, atmospheric effects and depth-of-field degradation. The handbook can be applied to the selection of surveillance systems as well as a broad range of photo-optical instrumentation tasks.
In February 1976, Itek was requested by the office of Attorney F. Lee Bailey to perform image analysis on photographs of a robbery at the Hibernia Bank in California. The desired objective in pursuing the analysis was to make the facial features of Mr. Bailey's client, who is shown in the bank film of the robbery, clearer and indisputable. This was desired in order to better judge what type of facial expression Mr. Bailey's client evidenced (e.g., either a smile or a grimace-like appearance) during her reaction to a shooting that happened during the bank robbery. We performed a digital, grain suppression, Fourier transform filtering operation on the subject's facial features, which suppressed the grainy appearance of the imagery but left the facial features virtually intact. The final product of this study was several pairs of before and after filtering comparisons of the facial features. The grain was effectively removed, and the expression made more identifiable. However, judgment by the observer was still required to determine the nature of the expression in some frames.
The purpose of this study was to perform analysis of the films that show the major events of the Kennedy assassination in Dallas in November, 1963. The two films that were studied extensively were: the Hughes film, which shows windows of the Texas School Book Depository Building (TSBD) simultaneously with the Presidential limousine a few seconds prior to the first shot; and the Zapruder film, which shows the limousine and occupants during the sequence of shots. Many image analysis techniques were employed. These included: digital image processing (integration, inverse transform filtering, and binary quantization), stereo-photogrammetric profiling, mensuration, photointerpretation, and coherent optical filtering. Each area of study was selected based on its relevance to current questions and uncertainties of the assassination. Each question was addressed with the most appropriate analytic techniques, hence the variety of image analysis methods used. The primary areas of study were: the TSBD windows; a bullet trajectory study and its relation to a "single bullet theory"; Governor Connally's reaction; dynamics of the fatal head wound and reactions; and questions on the "Grassy Knoll". No evidence of conspiracy was found from the study. In fact, claims of conspiracy based on these events depicted in the films were found to be lacking in substance.
A variety of infrared instruments have been developed for the detection of intruders. Operating on the principle that all intruders emit infrared radiation, sensors have been designed to detect this radiation. This paper describes a number of applications in indoor area protection and outdoor surveillance. Also discussed are the advantages and limitations of such systems compared with other technologies.
The currently used methods of fingerprint detection may be classified into two categories: those which are dependent on the adherence of inert materials to fingerprint residues (powder methods), and those which rely on chemical interaction of a detection reagent with specific components of the latent print (for example, ninhydrin method). Both classes, in fact all conventional fingerprint detection methods, require a chemical or physical treatment of the exhibit under examination.
This paper briefly describes a Proposed Standard for Monochrome Television Cameras for Courtroom Use. In this brief description the physical parameters (size, weight, marking, user information, etc.) are ignored, and the operational parapeters (format, sync signal, power requirements, connections, etc.) are mentioned only briefly. The performance parameters, 1) relative spectral response, 2) total response, 3) signal-to-noise ratio, 4) limiting resolution, 5) contrast transfer function, 6) shading and 7) geometric distortion, are described in some detail. Minimum acceptance levels and methods of evaluation are given for each of the performance parameters.
The most dynamic use of video recording techniques in the legal profession is to prerecord all testimony so that playing the prerecorded testimony to,the court or jury becomes "the trial." Videotape equipment is used to prerecord the testimony which is then edited by the judge in his chambers -- with his authorities close at hand -- and played for the jury in a logical, uninterrupted sequence. No longer need trials be delayed while counsel argue motions in chambers, nor do trials have to be rescheduled because a doctor, whose testimony is to be taken, is suddenly called into surgery. Nor do counsel have to make vague and uninformed opening statements because they do not know, or are unsure, what the evidence will show. The testimony can be prerecorded at the convenience of the witnesses and counsel. Moreover, the judge does not have to be present during the taping or while the testimony is played for the jury, as he will have seen the tape during his editing session. Where prerecorded trails have been used; they have relieved docket congestion, eliminated trial delay and shortened length of trials. The response from attorneys, litigants and jurors has been very favorable.
A new type of digital image memory and digital video processor is described. This unit, working at standard video rates and with a full frame storage capacity, allows low light level imaging thresholds to be reduced one to two orders of magnitude. With 12 bits per picture elements of memory plus non-linear output processing contrast, levels below 1% can be displayed. Applications of this equipment are also discussed.
Prior to March 1, 1971, the Congress of the United States had turned aside all suggestions that any form of electronic security was appropriate or necessary in order to protect it, and the millions who visited annually, against an act of violence. Even though some members of the House of Representatives were seriously injured in 1954 when a group of Puerto Ricans stood up in the gallery and shot down into the crowded chamber, it did not believe that electronic devices or bullet proof glass would be in keeping with its tradition. However, since March of 1971, thinking has changed and modern state-of-the-art equipment and devices are now used daily. A closed circuit television system of over 100 cameras, an intrusion detection system controlled by computer, and low dose X-ray package inspection systems are used at some of the entrances to the buildings.
Generally speaking, the Probeye Infrared Viewer has been used by many law enforcement agencies throughout the U.S. The names of these agencies which I will be quoting from have been omitted so as to not be misconstrued as an endorsement of our product. The following is what one agency found in the helicopter night patrol: "We found that it was very easy to locate vehicles with warm engines. This could be very productive in apprehension of industrial burglars during late hours. We had a unit check two vehicles which appeared to have warm engines. The first vehicle was warm, however, the second engine was cold; we had the unit recheck the second vehicle and he found a large dog in the cab. This was the only apparent heat source in the vicinity of the vehicle. We responded to a disturbance call in which a unit was holding three suspects. As we arrived, we were advised that there were possibly more suspects in the area. We scanned the area with the device and observed an object in a yard near the location. We directed deputies to the object and they found a suspect hiding under a hedge. The suspect was arrested for prowling. We were dispatched to the Lennox area to search for a kidnap-rape suspect on foot in a large field. Although we did not locate the suspect, we did locate and identify all of the searching deputies, numerous cats and dogs, and a large bag of fertilizer inside a greenhouse. We used the Probeye in the industry area on one P.M. shift. We found the device very useful for patrol work. The ability to search large vacant areas for suspects without turning on the light is a great benefit. Additionally industrial areas may be checked for suspicious (warm) vehicles. I feel it is a very valuable tool for our work