Cross = Photogrammetry

Question 1

Wouldn’t you agree that education is critical for the work that you do?

Answer 1

I think all education is important. That is why as a Forensic Examiner at the FBI we are required to participate in continuing education by attending conferences and participating in workshops. These discipline specific trainings are key to staying current in the field.

Question 2

You testified earlier that this is your first time in court, is that correct?

Answer 2

Yes, I stated earlier that this is my first opportunity to testify as an expert in court.

Question 3

Don’t you believe it would be better for my client, and the jury, to have a more senior and more experienced examiner testify in this case?

Answer 3

I think it is important to have a competent and qualified examiner testify in every case.

Question 4

Wouldn’t you agree that education and experience are vital to being competent?

Answer 4

Absolutely, education and practical experience are important.

Question 5

Are there individuals in your office that have more experience than you?

Answer 5

Yes, I have co-workers that have been with the FBI for more than 15 years. I have learned quite a lot from them. However, I have successfully completed an extensive training program that has prepared me to testify today.

Question 6

Do you consider yourself an expert?

Answer 6

I believe based on my formal education, training, and practical experience I am qualified to testimony to the results of my examinations. However, it is the role of the court to determine if I am qualified to provide expert testimony.

Question 7

Are you getting paid to testify?

Answer 7

I am paid for my time, and testifying is one of my job responsibilities. So, as far as compensation goes, it is the same as if I was spending the day back at the office.

Question 8

What does it mean to authenticate an image/video?

Answer 8

To authenticate an image and/or video means to determine if it is an accurate representation of what it appears or claims to be.

Question 9

What is the purpose of a forensic bridge or write blocker?

Answer 9

A forensic bridge or write-blocker is a device that allows incoming data but blocks all outgoing writes in order to preserve evidence. It also serves as a bridge between an external connection, such as a thumb drive, and an internal connection, such as your computer’s hard drive.

Question 10

What does it mean for an image to be conducive?

Answer 10

An image is considered conducive for a height determination if there is a frame that shows the questioned individual from the ground to the top of their head or headwear, in an upright posture, and that image has fixed foreground and background objects for camera alignment. Also, that there is sufficient resolution in the image plane.

Question 11

How can you be certain that you have the correct height?

Answer 11

Measurable variables are kept at a minimum by placing a person’s feet at the location in the live view, after the overlay has been achieved, in the foot placement of the questioned individual and by zooming in to choose the correct pixel that represents the top of the head of the questioned individual.

Question 12

You noted that the resolution is 3712 x 2160, is that a standard resolution?

Answer 12

Unfortunately, there is no standard resolution for recording devices. 4k or Ultra HD, refers to a display resolution that has a horizontal pixel count of approximately 4,000 pixels. So, while this recording has slightly fewer pixels than 4,000, I would still consider it 4k.

Question 13

What is compression?

Answer 13

Compression is the process of reducing the volume of data required to store or transmit information.

Question 14

Can you name and describe the two broad categories of compression?

Answer 14

The two broad categories are lossy and lossless. In lossy compression, the data is lost and cannot be retrieved in its original form. In lossless compression, no data is lost, and all the data can be retrieved in its original form.

Question 15

What is an I-frame?

Answer 15

In video compression, I frame stands for Intra-coded frame, meaning that they are coded without reference to any other frames. Because of this, they are often stated to contain an entire image.

Question 16

What is a hash in the context of digital evidence?

Answer 16

A hash is an alphanumeric sequence of numbers that specifically represents a digital file.

Question 17

Why do you use the black magic?

Answer 17

The black magic a media player that is compatible with the software we use that allows use to perform the overlay of the evidence image to the live image when we are on-site.

Question 18

What three things are generally needed to play a video file?

Answer 18

First, you must have the correct codec, which stands for coder/decoder. Codecs are responsible for encoding the video data into a smaller format, which is then decoded for playback on devices.
Second, you need a media player compatible with the operations system of the computer.
Third, you need a container file type that is compatible with the media player. The container file tells the player how to the play the media.

Question 19

What is metrology?

Answer 19

Metrology is the scientific study of measurement

Question 20

What is focal length?

Answer 20

Focal length is the distance, measured in millimeters, between the point of convergence of the camera lens and the sensor recording the image. The focal length dictates how much of the scene the camera will be able to capture.

Question 21

Does focal length affect perspective?

Answer 21

No, focal length does not affect perspective, it only changes the size of the image.

Question 22

Why was the aspect ratio not 4:3 or 16:9?

Answer 22

CCTV systems have no standards, so recording devices may output video at any ratio.

Question 23

Why do you put a person in the stance of the questioned individual?

Answer 23

Placing a person in the stance of the questioned individual helps to provide an estimate of the effect of posture on the height measurement, as well as helping to locate the position of the questioned individual.

Question 24

What are some examples of uncertainty that cannot be measured in reverse projection?

Answer 24

Some examples of uncertainty that cannot be measured in reverse projection are those associated with the footwear worn in the image, any headwear that may be worn in the image, changes in height that occur throughout the day. Generally, people are taller in the morning, as our spines tend to decompress as we sleep, and as the day progresses, gravity compresses the discs, making us slightly shorter.