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Forensic Rulers and Scales: Types, Characteristics, and Uses

Forensic Rulers and Scales Types, Characteristics, and Uses

You have to have accurate measuring tools, such as rulers, gauges, and grids for precise measurements in the forensic application.

But… Number of Options!! Thus, you should know what to choose.

Honestly, I recently made a wrong purchase— a digital product. I just lean down and make a purchase, compulsively. That ended in a product that didn’t meet what I intended for. This is also true for owning or using a forensic ruler and scales. 

So, you’re going to learn more about the measuring tools in forensic w.r.t.:

  • Different types of forensic rulers and scales
  • Their forensic applications
  • Best available options— in each section.
  • Tips to using them

Tabulated Summary: Different Types of Forensic Scales With their Uses

Forensic ScalesDescriptionsForensic Uses
ABFO No. 2L-shaped axis with distortion correction circlesBitemarks, injuries, shoe marks
AdhesiveRegular photomacrographic or ABFO No. 2 scale with adhesive sideVertical and overhead surfaces
Regular Photomacrographic2”, 6”, and 12” extended forensic scale with distortion correction circlesOne-axis measurement of various evidence on sizes
Horizontal & VerticalRight to left, and top to bottom scalingDistance photography
Tri-folds3 folds. 1 fold of 30cm and the other two makes 60cmShoe, tire, and blood spatter
Hinged L ReferenceL-shaped scale with an angular hingedAccurate measurement of angles made by shoe, foot, blood, etc.
Continuous RollsStripes of either repeating pattern or continuous scalesMeasuring longer evidences
Different Types of Forensic Scales With their Uses

1. ABFO No. 2 Photomacrographic Scale

ABFO No. 2 is an L-shaped scale designed by the American Board of Forensic Odontology (that’s why ABFO), specifically to compare a bite mark with human teeth. The main goal is to obtain a usable macro (1:1 or life-size) image of the bitemark to compare it to a reference sample.

Note: The term “photomacrographic” defines a photograph taken with a visible scale to the naked eye with a precise scaling even after photomacrographic magnification.

Types of ABFO Scales

It can be broadly categorized into four:

  1. Based on divisional values: Either 1” or 1cm metric scales.
  2. Based on material value: Papered, transparent plastic or glass, flexible plastic, yellow wooded, and Magnetic
  3. Based on Quality measures: gray, black, white, yellow, and fluorescent (in UV lightings)
  4. Based on Axis length: Equal sized (most common), one-elongated axis (for shoe prints).

Characteristics of ABFO Scales

The build has precise 90° corners, 3 circles, and crosses. This all sums up as the most ideal choice for distortion-free scaling— as soon as forensic evidence fits inside the longitudinal and horizontal axis.

ABFO No. 2 Photomacrographic Scale
  1. 3 circles: useful in compensating for distortion resulting from oblique camera angles.
  2. 90° corner: 1” width of horizontal and longitudinal axis forming 90° corner. 
  3. Black and Grey Stripes: Alternating black and white bars helpful in measurement of grossly over- or under-exposed photographs. 18% gray stripes are for color corrections.
  4. Metric Scale: 1 cm metric divisional lines (common). 1 inch divisional lines (not common, but available at forensicssource.com).

Forensic Uses of ABFO Scale

Though they were only made to assist bite marks documentation, they are now used for various purposes. For instance, it can be used in

  1. A large ‘L’ shaped scale is used for shoe marks photography
  2. Injuries and bruises to the skin
  3. Marking or blood spatter patterns on surfaces, and so on…..

Best ABFO Scale to Buy

If you want to buy one, you should first decide which one to buy. The most common ABFO No. 2 scale is metric (mm divisions) with black-white stripes and a color correction slip of 18% gray scales.

And let’s say, your work deals with dark rooms, alternative light sources, or UV, you can go with a fluorescent-based ABFO scale. In addition, if you’re a document examiner, having a black or gray photo macrographic scale would be ideal.

For forensic labs, it is recommended to buy at least five different ABFO scales named: regular-white, black, yellow, magnetic, and fluorescent. And for forensic students, you’re good with one regular white “L” shaped scale.

Read More: Forensic Photography & Scales: How To Use Them Effectively With Examples

2. Adhesive Scales

They are, as the name suggests, adhesive.

But not like “fixed.” They are more semi-sticky and can be easily removed once the work is done. After removal, branded forensic adhesive scales do not lean any adhesiveness to the surface, which is critical for preserving the evidence’s integrity.

Forensic Uses

They are non-reusable and are mostly used for documenting vertical and overhanging surfaces where standard scales are difficult to use. Examples: photography evidence on walls, ceilings such as spatter marks, bullet holes, fingerprints, etc.

Types of Forensic Adhesive scales

It can be divided into four major scales. These are:

  1. Metrics divisional value: either 1” or 1cm metric scales.
  2. Based on color: white, gray, black, or fluorescent (yellow, green)
  3. Either flat short metric, or continuous roll peel-off stripes.
  4. Continuous adhesive scales:
    • Series of identical metric scales on a roll. Eg: repetition of 10cm long scale on roll separated with small gaps.
    • A long series of metric scales. Eg: a long continuous 100cm adhesive stripe without any gaps.

Characteristics of Adhesive Scales

They are flat (or roll) flexible printed stripes of different colors like a normal scale except one side is adhesive to settle beside the evidence that is being processed for a photograph or forensic analysis. 

There are also adhesive scales based on ABFO No. 2 that are mostly in the shape of cards with peel-off sides. In short, it can be any scale with opposite adhesive sides.

Advantages: (1) More easily to use than regular forensic scales, (2) No need for an assistant to hold the scales, and (3) Leaves no traces or stickiness to the surface.

Drawback: The major drawback is uneconomical. As they are disposable (sometime after the first use, and sometimes multiple uses) it increases the overall cost when compared to non-sticky photomacrography scales.

3. Regular Photomacrographic Scales

Most regular scales are made from Vinyl, a form of plastic. You called them a plastic scale that is strictly made for forensic use. However, they are also in the form of metal or cloth tapes.

They have a metric (cm) and fractional (inches) divisional values on either side. They are mostly available in three sizes: 2”/5cm, 6”/15cm, and 12”/30cm with non-glare color options: white, gray, and yellow.

Characteristics of Regular Photomacrographic Scales

Regular Photomacrographic forensic Scale

So, how the forensic scale is different from regular stationary scales. (1) Forensic scale has photographic referencing stripes usually in black-white, and (2) circles (like crosshair) for compensating photogrammetry correction. (3) Vinyl plastic scales can be yellow, white, or transparent while metal and cloth scales are major yellow colors.

Forensic Uses of Photomacrographic Scales

You named it, it is there. They are the most widely used to photograph the evidence as a measure to provide dimensions. Their combination— usually two— is used as ABFO scales.

  • 2” scales: bullets holes, bullet, and cartridges 
  • 6” scales: photographing small and medium sized evidence.
  • 12” scale: medium to large evidence such as tire tread marks.

Note: Most of the vinyl scales have small-sized scale values that require close-up photography. For distance photography, large-sized values are employed called horizontal and vertical scales.

Who should buy it?

Everyone, if you’re a forensic student, no matter which field— except toxicology—  you should have it. And if you’re an agency you can even inscribe your company logo to it. Try Forensicsscource.com.

4. Horizontal and Vertical Scales

They are similar to vinyl ones except:

  1. only one side scaling,
  2. non-vinyl,
  3. scale values are larger,
  4. no/one crosshair circles, and
  5. only yellow color option.

In horizontal forensic scales, the scales are in inches (12” is common) and numbers are printed from left to right. While vertical ones are printed from top to bottom.

Both scales have a hole (or with or without crosshair) at the beginning, which can be used to make a hinged scale or as a hanging option.

Forensic Uses: Used in distant photography— aids in cs reconstruction as it allows reading of the scale from a greater distance.

5. Tri-Fold Scales

3-part foldable scale that is also compact as a 30cm long scale. It has Each tri-fold scale has 3 parts with two face scales (white and black shades).

  • First fold (x-axis): 30 cm (12”) long scales (from 1 to 30 cm).
  • 2nd- 3rd folds (y-axis): Linearly joining 2nd and 3rd folds constitutes y-axis. Numbering on the 2nd fold goes from 1 to 30 cm followed on the 3rd fold from 31 to 60 cm (total of 24”).
  • All 3-Cojoined: Has easy-to-read graphics and can be conjoined to form a single straight 90cm or 36 inch scale with black stripes for distant photography.

This unique arrangement makes it usable on a large L-shaped scale but not like ABFO No. 2. Why? Because the corner of ABFO scales is exactly aligned at 90 degrees. But due to non-measurable hinged in tri-fold scale, aligning it perpendicularly is quite not feasible.

Another question: Why y-axis isn’t built on a singular 60-degree scale instead of two folds? Because to make it compact so it can easily fit in a cs kit.

Forensic Uses: Used for tire marks, blood patterns, and shoe marks.

Read More: Forensic Photography & Scales: How To Use Them Effectively With Examples

6. Hinged L Reference Scale

Hinged scales are a type of fold scales except they have only two arms— one is longer than the other. They have smaller scales hence not be used for distance photography of evidence.

Forensic Use: Photographic documentation with angularity measurements in shoes, tires, blood patterns, and footprints.

Characteristics of Hinged L Reference Scale

  • Two faces: Black scales on white background and white scale on black background.
  • Smaller size writing on scale
  • Two folds with one arm 30 cm and second arm of 60cm
  • Has crosshair circle for photographic collection
  • 18% gray with black and white stripes 
  • Angular hinged movable short arm makes angular measurement easy.

Commercially available products: Reversible L Reference Scale, and Hinged L-reference scale.

7. Continuous Scales Roll

They are of two types. One is a normal yellow color continuous roll scale. And the other is photographic continuous scales. Both are available in feet length (100’ common) with each blade side having cm+mm and inch scales. 

Non-photo macrographic rolls are as simple as the regular roll. While in photomacrography scales, there are assisting elements such as black/white and 18% gray strips with crosshair circles. 

Furthermore, as stated in adhesive scales, continuous photo macrographic forensic scales are of two types:

  1. Continuous measuring values ranging from ‘0’ to a few hundred feet (100 to 300 feet). Usually non-adhesive
  2. Repeating scales pattern of 5cm, 15cm,and 30cm in a continuous roll. Usually have adhesive sides.

Forensic Uses:(1) Adhesive striped string rolls assist in vertical and overhead photography. (2) Long rolls employed in measuring the parameters dimension of cs.

Commercially available products are: Fiberglass Reel Measuring Tapes and Steel Measuring Tapes

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