Video makes the case

Chicago's approach to video enhancement helps solve crimes


     At this point purists might ask, "Where's the SDI (analog to digital) converter?" or "How are you going to handle multiplexing?" and "If you're going to take a nonlinear approach to forensic analysis, you're doomed!" The most honest and straightforward response to these statements is that necessity is the mother of invention. While sophisticated equipment intended to resolve some of these issues can be purchased, this equipment is expensive. Chicago's solution involved an ad hoc approach to needs, using equipment and capabilities it already had.

     Pinnacles' Studio 10 and Adobe PhotoShop SC are the principle software used in the 16th District design. Studio 10 is used exclusively for VHS tapes to capture sections of video related to an incident. Once captured, the event may be saved as an avi file that can be reviewed on any number of viewers including MMP. Additionally, Studio 10 allows the user to capture still images from the video by using tools provided from the program's pull-down menu. The stills are saved as JPEG files, which are suitable for PhotoShop enhancement.

Chicago's enhancement process
     Acquiring the recorded event from a crime scene is often accomplished with the help of personnel trained in downloading video files from the victim's system. It is a good practice to witness and note the steps used in this procedure as many source machines employ variations of the same process using different steps and passwords. It should be noted that digital sources copied to disk are not the original recording which, in fact, stays with the machine. Analog or VHS tapes are the original source and, when possible, should be duplicated for use in video enhancement. Using secondary sources, or copies, of the original source has important implications for the evidentiary chain.

     Captured stills enhancement from DVR or CCTV systems is slightly more involved. The instructions provided here apply to systems using Microsoft Windows XP. The process initially involves inserting the video source disk into the machine's DVD player and waiting a moment. An information screen should appear offering users a variety of options related to the inserted disk. It is important that the disk is recognized here, which is a positive first step. Users then close the information screen and right click on the start menu. This prompts a display to the left, which shows the computer's contents, including what is in its DVD drive. A double click on the DVD icon, and the disk's contents display to the right of the screen. The contents provide information related to the types of files on the DVD. Most of the files will be named or numbered and include extensions that identify file type. The disk also may display the viewer used to open the files. A viewer will appear as an icon, which is distinctly different from the other files. If this is the case, users simply double click the icon and the viewer codec loads to the system. Once installed, users open the viewer and select the browser option to locate the DVD file for review.

     In some instances, although the files are evident, there is no viewer icon. Here users must open Windows MMP and attempt to play one of the files from the disk. If the file won't open, the user will be prompted that help is available via the Internet. Because the file extension type is known, users can seek assistance according to the extension or download other viewers, such as Win Amp, that have strong codecs capable of opening several popular files. In most instances, downloads are free. With a little practice, this exercise will prove invaluable to resolving codec issues. And once four or five codec viewers have been installed, they typically can handle the majority of video sources encountered by police.

     Like Studio 10, several viewers have capture options that allow users to take still shots from the video source, though this is not always the case. Adobe's PhotoShop, however, offers a viable solution that can be accomplished in two sets of steps. First users must locate the print screen button on the keyboard display. During the play of an open file on any viewer they may press this button and hold the screen image into memory. Now they open PhotoShop and select "New" from the File pull-down menu. A screen will appear and users simply press "OK." The next screen that appears will be blank. Users then go to the Edit pull-down menu and click on "Paste." This places the captured screenshot in the blank space but users are only concerned with the photo image display on that screen. Users then choose the dotted square icon from the PhotoShop toolbar to the left and drag the square from corner to corner over the section to capture. Users then return to the Edit pull down and select "Copy" and repeat the steps in italics above. This image should be saved in a folder related to the event as a TIFF or JPEG file. The file naming conventions selected are ultimately up to the department, but short names, numbered in sequence, are the easiest to remember.

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