SRU chemistry researchers crossing the line into forensic analysis of ink
Heather Kane, a Slippery Rock University senior chemistry major, cuts samples of crossing ink lines drawn on a paper that are being used as part of a study to that could provide forensic analysts a better option for their investigations.
Sept. 9, 2021
SLIPPERY ROCK, Pa. — Handwriting analysis is a critical part of forensic investigations. Detecting forgery and the order of signatures on signed contracts are examples. But these issues aren't easily solved by typical visual or microscopic analysis. Researchers at Slippery Rock University are conducting a study that goes deeper, albeit paper thin, but enough to potentially change the way that forensic document examiners look at ink strokes.
Andre Braz, an assistant professor of chemistry, and his student, Heather Kane, a senior chemistry major from Butler, are literally taking a different view by cutting the paper and analyzing the physicochemical interaction between two ink lines crossed on paper from a side angle. They are using a technique that requires an instrument called a Raman spectrometer that provides detailed chemical information about the inks.
"The order of two crossing lines is one of the most difficult things to answer in forensics," Braz said. "A lot of forensic analysts are reluctant to go beyond the microscope. Most of the cases they cannot solve visually, especially these days with pens tending to have more similar chemical compositions. You really need to start using chemical analysis and not all of the forensic labs are equipped with that. They have to go to a chemistry lab."
That's where the SRU researchers come in, using the chemistry lab at SRU as well as the University of Pittsburgh's Materials Characterization Lab to access an automated Raman spectrometer, which magnifies by 20 times the ink-absorbed paper, providing a chemical image of the inside of the ink crossings with more than 300 data points within a tiny segment.
Braz compares the chemical images of crossings obtained with the Raman spectrometer to those of the brain obtained with X-ray or CT scans.
"The idea is to analyze writing samples chemically, which is more objective," Braz said. "We want to look inside to see how the ink is distributed."
Braz began developing his method while he was earning his doctoral degree in criminalistics from the Universidad de Alcalá in Madrid, Spain, from 2012-15.
In his research, Braz saw some interesting results with certain inks that can often fool forensic document examiners: the second ink stroke that crosses another appears, from a surface-level observation, to go underneath the first line.
"According to my hypothesis, when we're writing with a pen, the paper absorbs the ink, but once it encounters the other ink that is already absorbed on the paper, the pen doesn't write," Braz said. "The pen only continues to write until it contacts paper that will absorb the ink. We don't see the second line when it crosses the first line, even though we applied it last. What we're trying to find out through this research is, 'Do we see that pen's ink underneath (the first line), or don't we see that pen's line at all?'"
Braz enlisted the help of Kane through SRU's Summer Collaborative Research Experience grant program for $4,000, which paid Kane a stipend and travel expenses to Pitt's lab.
Kane is preparing more than 200 samples of crossing ink lines, each using one of four types of pens including Pilot, Uniball and BIC. Braz is using the same pens as those from his previous doctoral and postdoctoral research, which he conducted at the Universidade Federal de Pernambuco in Brazil before coming to SRU in 2019, so that samples remain consistent.
The researchers are also testing samples based on time elapsed between the drawing of the first and second lines of a crossing, which is important in forensics to determine the relative date of two signatures in a document.
Kane uses a scalpel to cut the paper samples at the point where the ink lines transect, and then the cross section of the sample is captured by the Raman spectrometer for analysis.
"This has been a great opportunity because I haven't used a Raman spectrometer before and it's awesome to branch out and do more while gaining new knowledge," said Kane, who learned of the project through her Introduction to Research class last year. "This is completely different than taking a lab as part of your course where you know exactly what you're going to do and you're expecting a certain outcome. With research, you might get something different than what you were expecting and there's a lot of bumps in the road that you have to adjust for."
"Heather had a lot of autonomy because she is preparing the samples from scratch," Braz said. "The skills that she learns while doing this are not just about the methods, but being able to do research with limited resources and still being creative and getting results out of it. Those skills will be valuable for her after she graduates, as well as broadening her range of using instrumentation by working in different labs."
There are several other instruments in the SRU lab that Kane and other students have the opportunity to use. They include infrared and ultraviolet spectrometers, gas and liquid chromatographers, and atomic absorption and atomic emissions spectrometers.
"We are well equipped at SRU, but for these applications with paper and ink, the best instrument would be non-destructive technique that is better for forensic applications (to retain the evidence)," Braz said. "Infrared is non-destructive but it detects signals from the paper and we're only analyzing the ink."
Later this month, Braz and Kane will complete the data collection phase of the research and Amanda Chaves, currently a graduate student at the University of Bergen in Norway who previously worked with Braz in Brazil, will assist in the computer analysis of the samples. The researchers plan to share their findings by publishing them in a peer-reviewed forensic journal next year.
They are hoping the results will support this technique for use in forensic investigations.
"Whenever you think of chemistry, some people think of these mad scientists mixing acids, but this is fairly simple," Kane said. "I also really like the idea that this could make a model for the world to use and benefit the justice system."
More information about chemistry programs at SRU are available on the department webpage.
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