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Archive September 2020


Forensic Audio-Video Analysis and Verification

Audio and video are the digitalized source of evidence that can be found at the scene of a crime or with the victim or the accused in the form of audio-video from mobile device or any CCTV footage. Such types of digital evidences are of utmost importance in civil or criminal cases. Therefore, audio and video forensics is the leading branch of forensic science in the digitalized era.

In forensic science, audio-video forensics forms three basic principles such as acquisition, analysis, and evaluation of audio and video recordings which are admissible in the court of law. One of the main tasks of audio and video forensic experts is to establish the authenticity and credibility of digital evidence. The forensic examination of audio and video is done in order to enhance the recordings to improve speech intelligibility and audibility of the sounds.

How the analysis of Audio-Video evidences are performed?

One of the primary tasks of forensic digital investigators to assist the crime scene investigators in order to find the conclusive proof via a number of scientific tools and equipments. After following the standardized procedure of crime scene investigation, at the time of evidence collection, the investigators must thoroughly search the suspected area and recover the evidence carefully. Such digital evidences must be protected from physical harm, environment, and heat.

Once the evidence is collected in a safe and secure manner, the proper documentation of evidence must be done in the form of notes or photography/videography. The documentation must include in which condition the evidence was found from the crime scene along with the name of the evidence collector, date, and time of evidence collection. All examination protocols are carefully examined and constructed for enhancement techniques that must be employed to the recovered evidence.

A variety of enhancement techniques can be employed on audio and video analysis. The techniques which are employed for video enhancement are as follows:

a. Sharpening: This step makes the edges of the images more clear and distinct.

b. Video Stabilization: This step reduces the amount of movement in the video, and also produces the fine playback.

c. Masking: This step covers the face or areas of the video that may protect the victim, witness or any law enforcement official.

d. Interlacing: In an analog system, the interlaced scanning is used to record the images or at the same time, this process is used to de-interlace which may be used to retrieve the information.

e. Demultiplexing: There is a device in CCTV named multiplexer, which is used to combine multiple series of video signals into a single signal.

The techniques which are employed for audio enhancement are as follows:

a. Frequency Equalization: There is a need for highly precise equalizers that are used to cut specific bands of frequencies. The frequency band which often contains more speech content is amplified or isolated. Large noise or interruptions can be analyzed by spectrum analyzer and the corresponding frequencies are reduced in order to reduce noise level.

b. Compression: Faint or low sound can be increased by compressing or leveling the signal so that the loud range can be minimized.

Such evidences are critically analyzed and listened carefully and proper documentation must be done. After standard forensic protocol, the forensic report is prepared by a forensic cyber expert and presented in the court of law.

The forensic audio-video  report must include the following details:

1. Results which were obtained from the analysis of audio-video files

2. Waveform charts of audio recordings and comparison waveform with formants

3. Identification of the format and type of recording

4. Type of processing which was used to analyze

5. Date and Time of analysis of audio files.

6. Description of the evidence in the type of circumstances and conditions in which it was collected

7. Description of the enhanced audio-video and type of software that was used.

8. Qualifications of the Audio Video Analyst.

9. Authorized signatory with name and stamp

10. Hash Values of the Audio Video Files.

Software for Audio Analysis
  1. WavePad Master
  2. Sonic Visualizer
  3. Praat
  4. Gold Wave
  5. Audacity
  6. Speech Analyzer


Cross-Examination of Forensic Experts and their forensic reports

Cross-Examination has the power to change the falsehood case into truth. According to Section 137 of the Indian Evidence Act, the examination of a witness by the adverse party shall be called his cross-examination.


Cross-examination aims to highlight discrepancies or inadequacies in the other party’s evidence. This type of examination also uncovers inconsistencies in witness declarations and to inspire realities that help in interrogating the case. The order of Examination is stated under Section 138 of the Indian Evidence Act which stated that the witness must be examined-in-chief, then the opposite party cross-examines the suspect, and if the suspect called by the party in desire, then it is considered as Re-examination.


There are two principle explanations behind conducting a cross-examination process:

a) to have the witness and give evidence that encourages you and your case, and


b) to ask the observer inquiries about any proof they gave before that you don’t believe is right.


The standards about interrogation aren’t as exacting as they are for direct assessment (when you question your own observers). For instance, in interrogation, one can:


 pose driving inquiries, and
 Challenge the other party’s proof (that is, attempt to show that it’s not dependable or right).


One of the major purposes of cross-examination is the revealing of truth and exonerates the innocent one. Another purpose is to distort or weaken the force of witness evidence. The objective of cross-examination is to challenge the credibility, accuracy, and general value of evidence presented in chief to shift the facts related to any case which is already stated by the witness to exposed discrepancies and illicit the true fact which will support the case of opposite party.

In cross-examination, the rules are not as strict as rules which must be taken into consideration at the time of examination-in-chief. In this, one can ask leading questions and also challenge the other party’s evidence in order to show that their evidence is not reliable. The most significant point for the witness to recall is that in such circumstances losing of temper is extremely harming to his bearing.

In most cases, however, the cross-examination of an expert witness is carried out along far more civilized lines, and the evidence is tested by logical questioning about the methods employed in the examination and about the validity of the conclusions reached.

From the perspective of the cross-analyst, there is a need to decrease the evidential estimation of the declaration to a point where the appointed authority or jury will view it as unsound, questionable, or even mixed up.

In the event that the end is sufficiently based, the questioning is probably going to fall flat, however on the off chance that it emerges from erroneous perception or thinking, successful addressing will uncover this.


An arson investigation basically focuses on four broad areas which are as follows:

 Proof of incendiarism: The proof of incendiary materials come from fire scene examination by the experienced forensic expert. With the use of comprehensive knowledge about the fire dynamics, fire investigators determine the root cause and origin of the fire.
 Proof of origin: The forensic fire investigators focuses on the origin of fire by thoroughly examined the crime area.
 Proof of motive: This majorly focuses on financial condition of the individual or the person who claimed his or her property, this also highlighted the profit as well loss from operations and cash flow.


A standardized protocol must be followed in arson and fire investigation which is as follows:

1. Identification of the first caller from the scene of incidence.

2. Identification of any injured person present at the scene of incidence and medical assistance must be provided to the personnel.

3. Protect the whole area by the barricading tape in order to avoid entry of unnecessary personnels.

4. Obtain photographs of the scene of incidence from all the possible angles.

5. Obtain insurance information and identification of the public or private insurance investigators.

6. Record check of the property is another crucial step by the forensic investigators. Record check includes assessor records or tax records.

7. Weather conditions must be taken into consideration as well as proper documentation of the scene of incidence must be taken in the form of notes.

8. Searching method must be employed by the forensic experts and crime scene investigators depending upon the area of the crime scene.

9. Remove all the debris and clean all the relevant tools or articles and establishing the area for evidence collection.

10. Evidences must be thoroughly searched and collected from the crime scene as well as preserved properly for the further laboratory analysis as evidences are admissible in court of law.

11. Analyze fire flow patterns, damage patterns, and evidences such as shields and shadows, inverted cone burn pattern, etc. Document the evidences with photos, sketches and notes.

The role of forensic fire investigator is to check for possible incendiary devices, license plate of automobiles in the area of fire, and to ensure that access to the scene is under control. Another major task of fire investigator is to survey the exterior as well as interior of the structure of the building. The goal is to assess probable fire origin, secure evidence and to control fire overhaul procedures to protect evidence.

Once the evidences are collected in secured manner, they will send to the forensic laboratory for further analysis and examination. After the results are interpretated, the report prepared by forensic expert is admissible under court of law.