PROBLEMS OF APPLICATION OF DIGITAL VIDEO RECORDING TECHNOLOGIES IN FORENSIC SCIENCE.
A.V. Kholopov,
postgraduate student of the Department of Forensic Science, St. Petersburg Law Institute of the Prosecutor General's Office of the Russian Federation
Information Security. Confidential No. 1, 2003
Modern digital technologies in the field of recording audiovisual information have reached such a level of development that the prerequisites for using these technologies for forensic purposes are being created.
Digital methods of recording information have now surpassed analog means in many ways in terms of the quality of recording, playback and storage of recorded information.
The use of digital video recording to record factual information in forensics can be implemented by using a digital video camera and a portable computer during investigative actions.
However, when using these tools, a number of problems arise related to ensuring the evidentiary value of the recorded data.
The problem of proof when using digital video recording to record information during investigative actions is usually associated with the possibility of changing the recorded data using computer technologies, which leads to the inadmissibility of using this data as evidence in criminal proceedings.
Therefore, the main attention in the article is paid to such methods of digital recording of audiovisual information that exclude the possibility of uncontrolled subjective interference in order to change the data obtained during the investigative action.
In order to determine the possibilities and conditions for the admissibility of using the digital video recording method in forensic practice, it is necessary to analyze the principles of obtaining a digital video image and compare it with conventional (analog) methods of obtaining a video image.
A digital video camera is almost identical in design to a conventional one, the differences lie in the method of recording a video image.
Thus, in a digital video camera, the video image formed on the CCD matrix is converted from analog to digital and recorded on a video image carrier as a stream of digital data.
When preparing to use digital video recording to record the process of investigative actions, the question of choosing an information carrier arises, since today there are several standards of digital image carriers on the market, for example, Digital 8, Mini DV, Micro DV, which are cassettes with magnetic tape.
In this regard, it is necessary to decide which of the given types of digital video information carriers is more appropriate to use for forensic purposes.
It can be said right away that the question of choosing digital video information carriers should be decided between two standards — Digital 8 and Mini DV, since the Micro DV standard has not received widespread use.
The question of choosing between the specified types of digital video media is not fundamental, since both provide high quality recording, although in terms of cost characteristics they have a fairly large difference, due to the fact that the Digital 8 standard is also used in analog Hi8 video cameras, which makes these cassettes cheaper.
When choosing digital video cameras, it is also necessary to take into account what analog video cameras are equipped with the forensic department, since if SONY video cameras of the Hi8 standard predominate and there are a large number of video cassettes for them, then the choice of a digital video camera must be decided in favor of the Digital 8 standard.
It should also be noted that when deciding on the choice of a digital video camera for forensic purposes, it is necessary to take into account their compactness. Compared to Digital 8 video cameras, Mini DV video cameras are more compact, which is explained by the small size of the digital video image carrier.
When choosing a digital video camera for use in forensic purposes, it is necessary to take into account that digital video cameras have a number of capabilities that can greatly facilitate the process of video recording of the course of investigative actions.
This is especially true for video recording of investigative actions carried out in open areas (inspection of the scene of the crime, verification of testimony on the spot, investigative experiment).
For example, in most cases, video recording of investigative actions carried out in open areas is done handheld, which negatively affects the quality of the video image by shaking the picture.
All digital video cameras allow you to eliminate this drawback with the help of an optical stabilizer, which eliminates shaking of the video image when shooting video handheld.
When filming in open areas, for example when checking testimony on site, the quality of the audio sequence of the video image may be degraded by wind noise. A digital video camera (for example, Canon XM 1) allows you to use a corresponding filter (Wind Screen) in such a situation, removing wind noise from the overall audio sequence of the video image.
In addition to the above technical and forensic aspects of using digital means of recording information in investigative actions, a number of procedural issues arise regarding the use of these means in the process of investigating crimes, which is very relevant in connection with the adoption of the new Criminal Procedure Code of the Russian Federation.
Part 6 of Article 164 of the Criminal Procedure Code of the Russian Federation does not exclude the possibility of using digital means of recording audiovisual information in investigative actions as a technical means of recording traces of a crime: “technical means and methods of detecting, recording and seizing traces of a crime and material evidence may be used in investigative actions.”
The list of technical means used in investigative actions is contained in Part 2 of Article 166 of the Criminal Procedure Code of the Russian Federation: «During the conduct of an investigative action, stenography, photography, filming, audio and video recording may also be used.
The stenogram and stenographic record, photographic negatives and photographs, audio and video recording materials are stored in the criminal case.» Based on the provisions of this norm of the law, it should be said that the law does not establish a rule on the exclusive use of analog video recording methods.
If a video image is obtained using a digital method, then this does not mean that a digital video recording ceases to be a video recording.
From the point of view of the criminal procedure law, the principle and technology of forming photo, audio and video information is not important, but what is important is obtaining high-quality data that meets the requirements of Article 88 of the Criminal Procedure Code of the Russian Federation, that is, relevance, admissibility and reliability.
Thus, the use of digital video cameras as a means of recording during investigative actions does not fundamentally contradict the norms of the Criminal Procedure Code of the Russian Federation.
Of paramount importance is the issue of the reliability of digitally recorded video images.
Many legal scholars approach the issue of using digital technologies in investigative actions critically, and their opinions generally boil down to the inadmissibility of introducing digital video recording methods into investigative practice due to the possibility of making changes to recorded digital data using computer programs for editing video images.
M.A. Silnov speaks out against the use of digital video recording in the investigation of crimes, noting that “with the help of digital video and photo cameras, it is possible to superimpose a moving object on another background, change the visual properties of an object (for example, change the color of clothing), etc. already at the moment of recording, not to mention the subsequent processing of data in powerful graphic editing programs, by the way, on ordinary personal computers”1.
Indeed, the above opinion quite rightly points to the possibility of making changes to digital data obtained during the recording of the course of investigative actions by means of computer technologies. However, many forensic scientists positively consider the possibility of using digital video recording in investigative actions based on specially developed methods.
To exclude the possibility of computer editing of digital video images, the following conditions are necessary:
- after using the digital video recording, it must be viewed by the witnesses and other participants in the investigative action;
- immediate certification of the obtained digital data by the participants in the investigative action, in accordance with the requirements of Part 1 of Article 170 of the Criminal Procedure Code of the Russian Federation: «…investigative actions are carried out with the participation of at least two attesting witnesses who are called to certify the fact of the investigative action, its progress and results…» (if the investigative action is carried out without the participation of attesting witnesses, Part 3 of Article 170 of the Criminal Procedure Code of the Russian Federation, then digital video recording with subsequent frame-by-frame printing of images should also be used, and some models of digital video cameras allow taking photographs and recording digital images on a removable flash memory card);
- certification, packaging and sealing of digital video image carriers and their use as appendices to the protocols of investigative actions;
- exclusion from the software and hardware of recording means of editing digital data obtained during the investigative action; conducting a check for the absence of programs included in the computer software that allow changes to be made to the digital video image, with coding of the results of such a check, for example, with the digital signature of the prosecutor-criminalist.
An important requirement from a procedural point of view, aimed at ensuring the reliability of the data, is the need to attach digital video media to the investigative action protocol (Part 8 of Article 166 of the Criminal Procedure Code of the Russian Federation).
When using conventional (analog) video recording, video cassettes with a recording of the investigative action must be attached to the investigative action protocol.
As stated earlier, in a digital video camera, video recording is carried out on magnetic tape of Mini DV and Digital 8 standard media.
Using this type of video storage media as appendices to investigative protocols seems problematic, since the cost of such media is quite high.
Moreover, this type of media is reusable, i.e. the video recorded on it can be edited and rewritten again or the magnetic tape can simply be demagnetized, which is a loss of evidence in both cases.
In our opinion, this problem can be solved by using CD-RW ROM devices in a Notebook portable computer for recording disposable CD-R disks, onto which digital video images from digital video information carriers are to be recorded.
The digital video image is copied from the digital video camera to the computer hard drive by connecting the digital video camera to the laptop via the built-in Fire Ware IEEE 1394 interface card and is recorded onto a disposable CD-R disk.
At this stage, we encounter a problem of the following order.
The fact is that the maximum capacity of a disposable CD-R disk is 700 Mb, whereas when copying a 15-minute video image from a digital video camera to the computer hard drive in AVI format (without compression), the size of this file is about 1.5 Gb.
In this regard, when rewriting video from a digital video camera to a computer hard drive, it is necessary to use a method of video compression using video codecs, which will significantly reduce the size of the recorded video files and will not lead to a significant loss of quality.
In this regard, it is recommended to use video compression with the MPEG4 video codec using DivX technology.
This video codec for compressing digital video images is the most suitable for use in investigative actions, since it is important to record the process of investigative actions during video recording, which can last more than an hour.
Therefore, the MPEG4 video codec is currently the only video compression format of its kind that can achieve high image quality and the size of the resulting video file when compressing digital video images.
In other words, when using the MPEG4 video codec and setting the appropriate video compression parameters on a standard one-time CD-R disc with a capacity of 700 Mb, it is possible to record high-quality video images lasting about two hours.
Today, Hitachi has released a series of digital video cameras (DZ-MV100, DZ-MV200 and DZ-MV270) that are capable of recording digital video on regular 12-centimeter DVD discs and on smaller, 8-centimeter ones (Fig. 1).
When using such video cameras for forensic purposes, it is necessary to use DVD-R discs (disposable) rather than DVD-RAM discs, which will allow recording 120 minutes of video in standard quality on a double-sided DVD-R disc.
The use of such digital video cameras will allow you to avoid the procedure of transferring digital video to a disposable CD-R disc using a laptop. However, digital video cameras of this type are quite expensive.
Fig. 1. Hitachi MZ-DV100 DVD-format digital video camera
After recording the digital video image onto the disk, it is viewed by the participants in the investigative action, certified, packed and attached as an appendix to the investigative action report.
If the court requires viewing the video recording of the investigative action from a CD-R disk, then playback can be done using a portable computer connected to a video projector or TV.
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