The STL needs to explain why we know so little about the “unidentified man” in the Hariri assassination

Maroun Bou Sleiman
9 min readAug 24, 2020


Did the STL avoid identifying the man who pulled the trigger on purpose? Questions from a concerned Lebanese scientist.

Exhibit P198 from the Ayyash et al. case showing the recovered tooth of the “unidentified man” (obtained from the 18/08/2020 public judgement).

About me: I obtained my B.S. and M.S. in Biology from the American University of Beirut then a PhD in Molecular Life Sciences from the Swiss Federal Institute of Technology in Lausanne, Switzerland (EPFL) in 2016. I am currently a researcher specializing in genetics and bioinformatics in the Laboratory of Integrative Systems Physiology at the Institute of Bioengineering at EPFL.

Disclaimers: The views and opinions expressed in this article are those of the author in his personal capacity and do not reflect the views of his employer. As the author does not have special access to STL documents and exhibits, his views are solely based on information released to the public.

The trial of August 18, 2020 marked a milestone for the Special Tribunal for Lebanon as well as the Lebanese. The voluminous 2641 page judgement in the Ayyash et al. case was met with the political equivalent of mixed reviews. Some viewed it as a political victory as the STL clearly points to — but does not condemn — the political entities that had likely conspired to assassinate PM Hariri (namely the Syrian regime and Hizbullah).

At the same time, others ridiculed the fact that only Ayyash, a Hizbullah operative who is probably not the mastermind, was condemned in absentia after 15 years of forensic investigation by different local and international teams, witness and expert testimonies, trials, and most importantly almost one billion dollars of taxpayer money (actually less than that, but still).

So far, however, there has been little assessment of the judgement besides politically-driven praise, outright criticism, or some legal opinions. Most concerned the form and broad strokes rather than the technical content.

I went over the public version of the judgement text in an attempt to provide an honest scientific assessment as a concerned Lebanese citizen and as a scientist specializing in genetic data analysis. I focused on the parts that relate to the DNA forensic evidence.

Based on that, I identified an important avenue of the investigation that had disproportionately little coverage with less than 10 out of 2641 pages (0.38%) of the document dedicated to the matter: the DNA evidence from the “unidentified man”.

What we learn from the judgement text

In total, twenty-three people died as a result of the explosion including the presumed suicide bomber a.k.a. “unidentified man”.

All but three bodies were recovered from the crime scene, two of which were from members of Hariri’s security detail in the car closest to the explosion (may they rest in peace along with the other victims). They were so close to the powerful explosion that their bodies could not be retrieved but were instead identified using DNA profiling of human remains scattered in the crime scene.

A third set of remains was identified, scattered in a pattern consistent with someone being very close to and in front of the explosion epicenter. This fits with the theory of a suicide bomber driving the explosive-laden Mitsubishi Canter.

Examination of a tooth as well as DNA profiling suggest that this “unidentified man” is likely the suicide bomber and not Abou Adass, the man in the video falsely claiming responsibility of the assassination.

The investigation into the identity of that individual, however, falls short of the gravity of the crime, the scale of the investigation, and the people’s expectation.

In paragraphs 1426-1427, Professor. Ayoub, who is specialized in forensic odontology, was able to infer — from the analysis of one tooth — the individual’s gender based on morphological features as well as the age based on the colouring and lack of calcium deposits.

He added “that there was a distinguishing feature on the tooth — its surface shape was in the form of a spade, which is a feature rarely seen among the Lebanese”. Here, “shovel” is the right term in English and it seems to me that the conclusion was translated from a report in French (pelle). Finally, he concludes “that the tooth thus belonged to a 20–25-year-old man who was not Lebanese, or who had not lived in Lebanon for a long period before his death. Based on the DNA analysis and shape, Dr. Ayoub concluded that the tooth belonged to the unidentified individual whose remains they had found earlier.”

And that’s it, no more digging into this central figure’s mysterious identity!

The problem: is this all we can do with DNA?

Here we come to my main criticism on the DNA-based forensics. The claim of the suicide bomber being young, male, and most importantly not Lebanese is not revisited or confirmed using DNA evidence, at least not in the publically available information.

My impression upon reading and re-reading this section is that DNA profiling was used as a tool for comparison only. So the DNA profiles of remains of this individual were first compared to each other to establish that they come from one person, and subsequently to rule out the Abou Adass story but not to infer more characteristics about that individual (it is not clear if they inferred gender from DNA either).

So what more can we do with DNA?

Before answering this question, one has to understand how DNA can be “measured”. I will attempt to be the least technical here. I also want to note that while I am intimately familiar with DNA and genetics, I am not a forensics expert.

There are a multitude of ways to learn things from DNA, and the public STL judgement has no information on what specific techniques were used in what they refer to as “DNA profiling”. This is in stark contrast to the amount of introductory material explaining how a jamming device works, how a mobile network operates, how Alpha and Touch networks are specifically organized, and the file formats of their logs.

“DNA profiling” is taken for granted throughout the document. This not only hurts the geneticist in me, but also raises many valid questions and suspicions.

One of the most obvious things one can infer is gender. In the case of the STL judgement, it is not clear from the information if DNA is used to infer the “unidentified man’s” gender (although it seems likely). Remember that males have a Y chromosome but females don’t.

Then one can profile (not sequence) DNA using many methods that either “cut” the DNA at different places using enzymes, or make many copies of specific targeted regions, using another kind of enzyme with the now famous PCR method (sadly brought to fame by Covid-19 testing). Both techniques yield mixtures of DNA fragments of different sizes and abundances, unique to an individual.

The mixture is then loaded in a special “gel” and an electric current is applied. This leads to fragments with different sizes migrating at different rates, and consequently, each individual would have a “signature” pattern or profile — these are the famous bands we see in the movies.

These techniques, which do not actually read the DNA sequence, are standard and reliable methods of identification in the forensics world. To make any inference, however, one always has to compare two profiles.

In the STL case, profiles from very damaged bodies would be compared to DNA from the toothbrush of a victim or a relative to establish the identity of a victim. Or in the case of body fragments, establish the identity of the person from which the fragment originates.

This kind of DNA profiling is what seems to have been done, which is pretty standard, but this does not exploit the full potential of the genome — the full sequence of the 3 billion letters in your DNA!

DNA technology is in constant progress

To put things in perspective, DNA profiling in standard forensics (as explained above) was first used in 1986 and is based on very few informative features that form a unique profile — or “fingerprint” — for each individual (Panneerchelvam and Norazmi, 2003). The specific shape of this “fingerprint”, much like a real fingerprint, carries little information other than the fact that it is unique to an individual, yet the genome carries much more biologically- and forensically-relevant information.

On the other hand, the first (unfinished) draft sequence of the human genome was only published in the year 2000 after around 10 years of work involving hundreds of scientists.

Today, anyone can either sequence his whole genome or get information about millions of letters (genotyping) within a few weeks for much less than 1000 US dollars by simply sending a saliva sample by mail. A few months ago, I took a ‘Black Friday’ offer to sequence my whole genome!

Even in 2020, we are still far from a complete understanding of the human genome, or any genome for that matter. However, we do know quite more than what we did in 1986.

We can now predict, with varying reliability, traits such as eye color, skin color, hair color, height, facial features, baldness (Marano and Fridman, 2019).

In my line of research, I try to learn other things from genetic differences between individuals such as disease susceptibility or how we age. Could this unidentified person have a genetically determined disease requiring a specific medical treatment?

These predicted morphological features, much like an artist’s sketch, may be helpful in the investigation.

One can also learn about the ancestry of the individual from DNA. In the light of the STL judgement, and to complement or corroborate the forensic odontology report, this seems to be a very obvious thing to do. Does the DNA show, like the tooth, that the person is likely not Lebanese? If not Lebanese, then from what other ethnicity could that person be? The 3 billion letters may contain so much information that a damaged tooth may miss.

Finally, by looking at DNA methylation, an epigenetic mark, one can theoretically estimate the age of the individual. Methylation, which is a chemical modification on the DNA, changes in an expected pattern with age, and this is known as the ‘epigenetic clock’. This can further prove or disprove the claim about the age of the presumed suicide bomber.

Caveats on my remarks

To be fair, each type of DNA measurement requires a certain quantity and quality of DNA, which may not always be fulfilled. There is little mention of the DNA quality of the “unidentified male” but in all likelihood, the unpublished expert reports, would have covered these technical aspects.

The forensics work may be exemplary, but the judgement text may have failed to convey all the underlying work (whether unintentionally or on purpose).

Maybe some results were inconclusive or negative never made it to the final text. In this case, reporting these results may be a good idea.

In addition, some of the mentioned techniques are bleeding-edge and have been introduced to the forensics world later than 2005. If unavailability at the time is the culprit, one can still re-assess DNA, and ask it new questions to get more answers — unless the current outcome of the STL is satisfactory to the victims and their families.

Finally, while some DNA tests may satisfy a scientist like me, there are other considerations when it comes to the forensics and legal world. Assessing what is admissible in the case of the STL court is beyond my legal competence.

Concluding remarks

The elegant telecommunications evidence including the purchase, activation, and spatio-temporal cell tower usage is very convincing, yet it will never be as strong as direct evidence such as DNA from the crime scene.

The mystery of the unidentified man seems to be at best underreported or at worst purposefully underplayed.

I cannot help but wonder: could the identification of this man lead to damning physical evidence to directly incriminate Ayyash, the other defendants, and maybe others? What if this leads to some “red lines” that cannot be crossed?

In any case, the STL should reach out to the public to explain and clarify any ambiguity that arises from this scarcity of information on such a core element of the crime.

References for further reading

The STL judgement:

Marano, L.A., and Fridman, C. (2019). DNA phenotyping: current application in forensic science (Dove Press).

Panneerchelvam, S., and Norazmi, M.N. (2003). Forensic DNA Profiling and Database. Malays. J. Med. Sci. MJMS 10, 20–26.



Maroun Bou Sleiman

Researcher specializing in genetics and bioinformatics at the Institute of Bioengineering at EPFL, Switzerland