Determining Handedness in Handwriting

by Joelle Steele

As a forgery detection expert, I have studied many handwriting samples over the past 40 years, including signatures on checks, receipts, and contracts; holographic Wills; diaries and manuscripts; letters and postcards; filled-out forms; and even a handwritten book of recipes. And not all of these documents were in English. Detecting forgery is about comparing the handwriting details in a questioned document (the suspected forgery) with three or more authentic handwriting samples to see if the questioned signature is also authentic. These comparisons can be done in any language.

Determining handedness can be critical in implicating or acquitting a suspected forger or other criminal, such as a shooter. This may explain, at least in part, why handedness has been the subject of so many articles and scientific studies. But the main focus of most of these studies is on the handwriting slant alone, also called the horizontal stroke.

Many people, including some experts, assume that the handwriting slant will indicate a writer’s handedness; a right slant meaning they are right-handed, and a left slant meaning they are left-handed. But this is not a reliable assumption, because slant can vary from one person to another regardless of their handedness.

Slant is measured in degrees from the horizontal base line using a protractor. A slant that is less than 90 degrees indicates a right-hand slant, and more than 90 degrees is a left-hand slant. A vertical, non-slanted handwriting would be 90 degrees, but usually falls between 85 and 95 degrees.

According to those who have studied handedness, lefties are in the minority – about 10-12 percent, which means 88-90 percent are righties. This statistic even turns up in countries that use ideographic languages, such as China, which relies on symbols rather than letters to convey ideas without being associated with phonetic sounds (and is written right to left). But how were these percentages determined? They are quoted pretty much everywhere, but are they reliable statistics? Maybe, maybe not. The only thing known for certain is that left-handed people are in the minority wherever in the world handwriting is being used or studied.

The problem is that not every left-handed person writes with their left hand, not every right-handed person writes with their right hand, and some people are ambidextrous – estimated to be the case with less than one percent of all people, including me, the writer of this article. I can do everything with either hand equally well, except handwriting at which I’m 100 percent lefty. But I’m right-slanted when writing cursive, non-slanted (upright) when printing, and a non-slanted combination of cursive and printing when I’m taking notes in a hurry.

So, what about people who are right-handed? Is their handwriting always right slanted? Definitely not. Just a few weeks ago I examined a cursive signature of a righty. It was a 75-degree left slant. I have also examined about 30 or so cursive signatures and bodies of handwriting by right-handed writers who slanted to the left by about 80-85 degrees.

Some of a writer’s slant can be attributed to how they hold their writing instrument and how they position their hand when writing. Felt-tip, ballpoint, roller balls, and fountain pens, as well as pencils in varying degrees of softness, can also affect the degree of slant. Each writing instrument will impact with the paper differently too, and that affects how the writer holds the pen. For example, ballpoints can be held at whatever angle is comfortable for the writer. So can the felt-tip pen. But fountain pens and roller balls release more ink to the page, and writers who use those writing instruments will hold their pens to accommodate that additional flow of ink. In addition, fountain pens (now becoming a thing of the past for most people) must be held at the precise angle dictated by the pen’s tip for the ink to flow properly.

As for how the writing instrument is held, this can also vary according to how each individual holds their pen or pencil, regardless of the type of pen or pencil used, and regardless of their handedness. While most experts believe that right-handers hold their pen or pencil “correctly” and left-handers do not, right-handers don’t always adhere to the “accepted” way of holding a pen or pencil either, and some of the worst handwriting I’ve ever seen has come from the pens of right-handers.

As a left-handed writer, I hold my hand in the same position as a right-hander, hold my pen between my middle and ring fingers rather than between my index and middle fingers (although I do the latter if I hold a pen or brush in my right hand), and I don’t curl my hand or turn the paper. Contrary to what some experts say about this method resulting in illegible handwriting, my slant is to the right and my handwriting is perfectly legible and “normal” in appearance. One of my lefty clients also holds her hand like a righty. But her writing, while very legible and in all ways normal, does not slant at all, and is almost exactly 90 degrees vertical.

But enough about slant. As a forgery detection expert I analyze and compare handwriting under high magnification. This allows me to see the finest details of a person’s handwriting, including the probable direction in which the writing instrument was held. I can also better focus on the letter forms and how little things such as i-dots, t-strokes, and diacritical marks (diacritics) are made and placed relative to the letters. They can all have the potential to reveal a possibility for a certain handedness, but mainly they help me identify or rule out a suspected forger. If I can also determine an almost certain handedness in a writer, that could be of use if it helps identify a criminal.

Last modified 12/02/2020