Archive for the ‘Photography’ Category

In Photography and Video – We Want the Original Images

Jul 14th, 2011 - Filed under: Blog, Expert Witness, Image Analysis, Photography, Video Analysis

It always surprises me how often retaining attorneys send me digital copies of scanned color laser prints of photos in PDF format, or transcoded video files to do an analysis. Sometimes these images resemble their originals – sometimes they are a far cry from them.

To do the best enhancement, analysis, or authentication possible, originals are needed. Exact, logical copies of digital evidence is fine if the originals are digital.

With photographs, the original is the digital file as it came from the camera, or the negative from a film camera. If it’s a PDF, it is not the original.

With security digital video recorders, the original is an exact copy of the original data recorded by the DVR. If the file plays on a standard DVD player – it probably isn’t the original.

Determining if the still photos or video files are originals does involve more than simply determining whether the video plays on a standard DVD player, or if the still image file is in a JPEG file format – but those are good starts.

Whether you are using an expert or not – start demanding exact copies of the original visual evidence in your cases – it will make a significant difference in what that evidence can tell you.

Reflecting back on 2009

Jan 3rd, 2010 - Filed under: Blog, Certification, Image Analysis, Photography, Training, Video Analysis

When I think about the past year, and cases I’ve worked, training I’ve received, training I’ve given, there are a few things that stand out.

In the arena of cases, I had two unique experiences – A Daubert Hearing in 12/08, and Grand Jury testimony in mid-2009.

The Daubert Hearing was on image authentication (are the images real, and do they represent real people and real events). That hearing was U.S. v. Frabizio in December of 2008, and was one of the few Daubert Hearings on photography, imaging, or image authentication. It was an interesting case, as it was going to its third trial. I was retained by defense counsel to analyze and interpret the government expert’s report and findings. I provided information to the defense attorney on this report, and attended the Daubert hearing, and answered her questions on his testimony. With the limited number of Frye and Daubert hearings on forensic photography, forensic image analysis, or image authentication, it was an interesting experience to participate in this hearing.

The Grand Jury testimony was also on an image authentication case. In this instance, I was an expert witness for the government. I have testified in cases since the early 1990s, but this was my first time to testify before a Grand Jury. It was quite interesting, as there is no judge, no defense attorney, and the accused is not present, nor is a case detective. It’s the prosecutor, a court reporter, the members of the grand jury, and the witness. In this case, I was impressed by the professionalism of the prosecutor and the members of the grand jury – I can imagine a situation in which a system without the formality or presence of a judge, defense attorney, etc. moving toward chaotic – I was pleased that this was far from the case.

As to training I received, it would be a toss up between two classes I took in the field of photogrammetry. One was on reverse projection photogrammetry that I posted about earlier. The other was a class in using Photomodeler (a software application for applying photogrammetry) for close range photogrammetry, presented by Dan Mills of DCM Technical Services. Photogrammetry is taking measurements from photos, and there are several approaches to this technology. Unfortunately, there are very few classes available in close range photogrammetry or in reverse projection photogrammetry. I was fortunate to get excellent training in each in 2009.

Regarding training that I provided – it’s difficult to isolate any one specific workshop. But, I did have the opportunity to give four workshops in digital photography to the San Francisco Police Department in 2009. That agency purchased Nikon D700 cameras for their crime scene investigators and wanted each member to be trained in the use of that camera for crime scene and evidence photography. I was proud to be the trainer they chose to provide this instruction. We held four, three-day sessions, with eight investigators in each session. It was a pleasure to work with this agency and to see their dedication to providing their front-line personnel with the tools and training to do their job.

Lastly, another highlight of 2009 was being appointed chair of the Forensic Photography and Imaging Certification Board of the International Association for Identification. It is an honor to have been chosen to fill this position, and our board is working hard on several projects.

The last year was successful in many ways – looking back at a few of the highlights helps see where we are today and prepare for the future. I’m looking forward to more interesting cases and great training opportunities in the coming year.

G

Reverse Projection Photogrammetry

Nov 22nd, 2009 - Filed under: Blog, Image Analysis, Photography, Video Analysis

The Law Enforcement and Emergency Services Video Association (LEVA) held it’s annual conference this week. I was fortunate to attend the two day pre-conference workshop on reverse projection photogrammetry presented by Richard Vorder Bruegge, Walter Bruehs, and Chris Iber, all from the FBI Forensic Audio, Video, and Imaging Analysis Unit.

Reverse Projection Photogrammetry is used to measure objects in a photograph or video. It can be used to determine if an individual could be excluded or included as a suspect based on height. In addition to using this method to determine the height of an individual in an image, I have used this technique to determine the position of objects in relation to their surroundings (after the objects were removed), the distance of safety barriers in construction scenes (after the construction was completed and the barriers removed), the size of cracks in a sidewalk (after the sidewalk was repaired), etc. from photos of those scenes.

The workshop covered issues related to the methodology and foundations of this technique. Any forensic image analyst or forensic video analyst who hasn’t yet had the opportunity to take this workshop should do so. It has been offered at the LEVA conference for two or three years, and also at the IAI Annual Conference.

So, What’s the Story on Resolution?

Nov 5th, 2009 - Filed under: Photography

My post on Synchronizing Video has generated a few comments related to image resolution. Three people, all of whom have a significant background in forensic imaging, have made rather divergent comments. Multiple topics are being addressed, from crime scene, accident and evidence photography to latent print photography to SWGFAST guidelines/requirements to the resolution of video security camera systems.

In all of these, there is a common element regarding resolution – the image should have the resolution to see the details for the purpose of the analysis. In a crime scene, this may be enough resolution to see the relationship of different objects in the image to each other. In a fingerprint, this may be second or third level detail. In the security camera it may be enough to read a license plate or see individualizing features in an object or person.

In security video, I almost always wish there was more detail, or higher resolution. These images are frequently 640 X 480 pixels or less. In addition, they are often highly compressed, the camera is at a bad angle, the lighting is poor, the optics are poor quality and dirty, and the subject of interest is frequently in the distance. Very few in the forensic video analysis field would argue that we’d all prefer security video with more resolution.

In fingerprints, I have seen some pretty good prints at resolutions as low as 300 PPI. The SWGFAST guidelines currently call for a minimum 1,000 PPI at a native resolution. So, can a fingerprint examiner use images that are less than 1,000 PPI or that may have been scanned with a scanner that interpolates when set to 1000 PPI? Of course they can – and they do.

Regarding crime scene, accident and evidence photography, many people compare digital imaging to film and suggest only using digital cameras that match the resolution of film. When I ask these proponents which film format (disc, 110, APS, 35mm, 6 X 6, 4 X 5), which film brand, which ISO, using which optics, whether they are concerned with tonal resolution as well as optical resolution, etc., they usually are unable to answer. There is nothing special about film that makes it a standard for measuring resolution.

When taking photographs, we simply need to know what level of detail is required, then be certain that we capture that level of detail. Arbitrary numbers, like the SWGFAST 1,000 PPI help us to guarantee that we are capturing enough detail, but we also need to understand that resolutions less than those recommendations don’t somehow become useless.

G

Certification in Forensic Photography and Imaging

Oct 26th, 2009 - Filed under: Certification, Image Analysis, Photography, Video Analysis

I frequently read Jim Hoerrick’s excellent blog, Forensic Photoshop. In his October 12 post, he brought up the issue of certification, and it prompted me to comment on that topic here.

One of Jim’s points is that some certifications are not based on real world issues, and the correct test answers may be wrong when applied to the real world. Jim also mentioned that what he’s heard related to the certifications of the International Association for Identification (IAI) is positive.

As the Chair of the Forensic Photography and Imaging Certification Board for the IAI, I thought it would be important to discuss a bit of our process. We have two parts to our testing for certification – a written test and a practical test.

The written test is based on two texts, that is intended to show if the applicant has the general knowledge of photography and imaging to meet the standard set by the IAI for certification. Our board reviews the texts and the questions every year to attempt to keep the test relevant with current technology and appropriate for the topic of forensic photography and imaging.

The practical test currently includes ten assignments, and requires that the applicant competently complete each of the assignments to pass. These assignments are as closely molded to real world assignments as we can make them. We are currently reviewing the assignments and the wording of them so that they continue to represent real world assignments, and so that the assignments are as clear and explicit as possible.

Our board is always looking for input and I invite anyone with input to contact me at any time.

G