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Posts Tagged ‘Evidence Retrieval’

18: Creating Video Work Product as an Audio Video Forensic Expert

Friday, February 27th, 2015

video work productVideo work product is a way to document forensic investigations, like evidence recovery, for reference at a later date. Processes and procedures are documented using a video camera by a forensic expert during a forensic investigation for future use. I have referred back to my video work product many times during the course of a case when I have questions later in the evolution of the case. There are a few different digital video recording platforms that I use when creating ‘video work product’. Each one of these types of systems serves a certain purpose in assisting with a forensic investigation as well as the investigative process.

I personally use the VIEVU LE2 and LE3 body worn cameras. My main use for this body camera in my investigations is recording my forensic process in the field. This includes retrieving evidence from different systems so I can review the video later and include in my report to support the authenticity of my work product and any evidence used in the case.

Another type of digital video camera that I use to produce video recordings is a HDSLR photography camera. In some investigations, a single video recorded perspective may not be sufficient to display the forensic process or document the events. Having another high quality camera with flexibility of perspectives and interchangeable lenses can capture aspects of my investigation that body worn cameras cannot.

Video evidence produced by CCTV systems can help solve crime, as well as reproduce accidents and disasters as they occurred for play back in many different settings. A significant use a video forensic expert has when recording video from a CCTV system is to create an exemplar. This recording is used as a comparison file to the original evidence to help determine the authenticity of the original evidence.

It is a best practice of ours at Primeau Forensics to video record many forensic investigations like the exemplar creation process and evidence recovery so if anyone has any questions during the life of the case, this video work product can be referenced.

Now listen in with Audio and Video Forensic Expert Ed Primeau as he discusses creating Video Work Product for Forensic Investigations.

9: How to Recover Digital Media Evidence

Friday, November 7th, 2014

evidence retrieval I’d like to discuss evidence recovery, specifically digital media evidence recovery.  Having a forensic expert retrieve the evidence maintains the quality of the evidence and can help ensure that the original evidence stays intact on the original system so it can later be retrieved by other parties.  This is why it is extremely important that only a trained expert retrieve the evidence.  In this episode, I will cover proper procedures for evidence retrieval, proper handling of the evidence and what precautions one should take when retrieving digital media evidence from a recording system.

Steps for Proper Evidence Retrieval

1. Research before retrieving the evidence.  The forensic expert should learn everything they can about the recording system beforehand.  Connecting with the manufacturer, reading the manual and researching further online all benefit the expert.  This will make analyzing and operating the system onsite easier for the expert and optimize the retrieval process.

2. Obtain any necessary software, proprietary player or codec. If the system records proprietary or encoded files, the expert should obtain the player or codec beforehand.  If that is not possible, the expert should be prepared to install the necessary player or codec onsite from either the recording system or client.  More often than not, modern digital surveillance systems require a special codec or proprietary player and without this installed, the forensic expert will not be able to access the digital media evidence.

3. Record the evidence retrieval process. The forensic expert should record both audio and video of the evidence retrieval to include in the chain of custody and forensic report.  When I am recovering evidence from a digital recording system, I always have a VIEVU body camera on my person, as well as a digital audio recorder in my pocket.  Along with authenticating the evidence, this can serve as the expert’s notes later on in the investigation in case they need to refer to something that was discussed during the evidence retrieval.

4. Photograph and inspect the digital recording system. The forensic expert should include photographs of the unit in their report and take careful notes on anything they notice about the unit.  This could include damage, tampering or any other abnormalities they notice on the recorder.  Along with the video recording, it is usually beneficial for the expert to photograph anything they note during the process.

5. Follow the manual for the highest quality retrieval. The expert should have the manual with them when retrieving the evidence to make sure that any copy or export is in the highest quality format and does not affect the original recorded file.
photo credit: iLike iRiver via photopin (license)

7: Importance of the Chain of Custody for Digital Media Evidence

Monday, October 27th, 2014

chain of custodyEstablishing chain of custody when authenticating digital media evidence for use in the courtroom is extremely important. The chain of custody must account for the seizure, storage, transfer and condition of the evidence.  The chain of custody is absolutely necessary for admissible evidence in court.

Importance to the expert

My forensic software allows me to look at the metadata or digital information of an audio or video recording, but does not always allow me to understand how a recording was created.  Just because the information is missing from the metadata does not mean that a recording has been compromised.  This is why the chain of custody information is important to a forensic examiner. It helps show where the file came from, who created it, and the type of equipment that was used.  That way, if I want to create an exemplar, I can get that equipment, create the exemplar and compare it to the evidence to confirm the file properties.

Importance to the court

When I testify in court with a piece of evidence, I am always prepared with the chain of custody.  As I mentioned earlier, without a complete chain of custody, it can become very easy for the opposing attorney or prosecutor to challenge or dismiss the evidence presented.  Having a complete chain of custody form, as well as any other accompanying forms and including any visual proof of retrieval, such as pictures or video, greatly helps prove the authenticity and admissibility of the evidence in the courtroom.

Recently, new ways of establishing a chain of custody have come about and are slowly becoming accepted in the legal community.  Online services are now available for digital evidence that record the chain of custody and who has received the evidence.  The evidence is stored in cloud space and eliminates the need for repeated transference of physical copies.  It maintains standardized security procedures and is also useful as a backup storage space for surveillance cameras.

Chain of custody is important to the court because if I find something wrong with the evidence during the authentication process, it allows me to go back and determine who was responsible for the evidence up until that point. 

Importance to the investigation

The chain of custody is important to the investigation process because it is the first step when authenticating digital audio and video evidence.  Identifying this chain of custody provides information about whether or not this evidence has been copied or cloned.  As technology advances and becomes more accessible, digital media evidence has become easier to edit, modify and alter.  The Scientific Working Group on Digital Evidence (SWGDE & IOCE) defines Original Digital Evidence as, “Physical items and the data objects associated with such items at the time of acquisition or seizure.”  It is not always possible to receive the evidence from its original source at the time of acquisition or seizure.  Very often, I receive digital media evidence from a client who may have received it from the police or another source.  When this occurs, I have to pay careful attention to the reports, depositions and other legal documents that accompany the evidence.  This paper trail must be part of an unbroken timeline that shows exactly where the evidence has been between its creation and my examination of it.  When I encounter any gaps in this timeline that can raise questions to the authenticity of the evidence, further investigation becomes necessary.

There are occasions when I am asked by the client to physically retrieve the evidence directly from the recorder that created it.  This process creates the chain of custody for my investigation.  When an expert creates the chain of custody, it removes all doubt as to the authenticity of the evidence.   This process has become more common throughout my investigations when the original evidence is available for my retrieval.  To further authenticate this process, I create audio and video recordings of the retrieval process, which becomes part of the chain of custody. In addition, when I am at the site and I retrieve the digital evidence, I have access to the administrator information about that evidence, such as an administrative log, date and file info, and who accessed the files.  The more information an expert can retrieve strengthens the authentic chain of custody that is created.

Primeau Forensics’ chain of custody process

  • Save original package materials
  • Take photos of physical evidence
  • Take screenshots of digital evidence content
  • Document date, time and any other information of receipt
  • Ingest a bit for bit clone of digital evidence content into our forensic computers
  • Perform a hash test analysis to further authenticate working clone

All of the above information outlined in our forensic procedure for creating a chain of custody is important and necessary to include when creating a forensic report.

When examining digital media evidence, especially digital audio and video recordings, you should never examine the original file.  Always make sure that when you process a piece of evidence, you work on the copy of that file so that the original remains untouched at all times.  That way, if you have to go back to compare your work product to the original, you’ll have that original file preserved.

It doesn’t matter what forensic science you are an expert in.  The chain of custody is always important.  Maintaining that chain of custody is crucial for the credibility of your work product and eventual testimony.

 

 

 

 

 

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