Dental X-Rays and Age Determination

27 Apr

I got a heads up about this interesting case from my friend Julie Kramer.

It seems that Mahdi Ali will have to visit the dentist and get some x-rays done. Not because he has any dental problems but because he is accused of killing three men during a Minneapolis convenience store robbery this past January. He and his friend Ahmed Ali apparently entered the Seward Market one evening, guns in hand. Mahdi forced the two men there to lie on the floor, all this taking place in front of the store’s security camera. While his friend was near the rear of the store attempting to rob someone else, Mahdi shot the two men and a third man who walked in the door. He is now charged with three counts of first-degree murder.

His defense attorneys claim that Mahdi Ali was only 15 at the time of the shooting and not 16 as was previously documented. They state that he was born on August 25, 1995 in Kenya and that this would’ve made him only 15 at the time to the shootings. This is critical since if he were only 15 he will be tried as a juvenile, but if he was 16, he will be tried as an adult and if convicted will be subject to a sentence of life without the possibility of parole. Big stakes.

So Mahdi will trot off to the dentist for dental x-rays to help determine his age. But there are a few problems with this. Yes both our deciduous (temporary or juvenile) teeth and our permanent teeth do tend to develop in a known and fairly predictable pattern. Our various types of teeth appear at certain ages and are lost as permanent teeth develop on their own timeline. Taking dental x-rays in this teenage group can often help determine the age of the person. Here’s the rub — it’s not all that accurate.

If you just look at the age at which the eruption of wisdom teeth occurs, it can vary by as much as five years. Some people get their wisdom teeth early and others see them late. We’re all different. In this case we’re looking at only a few months that would straddle Mahdi’s 15th and 16th years. It will be interesting to see what the experts say in this case and how accurate they will attempt to be. The bottom line is that determining whether someone’s age is 15 years and 10 months versus 16 years and three months is almost impossible. Stay tuned.



12 responses to “Dental X-Rays and Age Determination

  1. Sir Emeth Mimetes

    April 27, 2010 at 10:30 am

    It fits with the modern assumptions about dating methods that they would attempt such a thing (although, biblically the whole case would have a different spin). People trust the assumptions in dating methods, even though they have been shown to be utterly unreliable.

    The same thing is true for ‘due dates’ in pregnancy and birth, and many other things that man tries to fit into a box. God’s creation is a bit too complex for that. 🙂

    Thanks for being honest about it!


  2. Jonathan Hayes

    April 27, 2010 at 9:18 pm

    Not attacking forensic odontologists (particularly here, where I don’t think an ethical odontologist would’ve proposed this as a valid method for age estimation), but the discipline has come under increasing scrutiny in recent years, particularly after the scathing assessment of forensics issued last year by the National Academy of Science. For me, forensic dentistry is at its most useful for body identification, where it’s just about as accurate as DNA, but effectively instant and very inexpensive.


  3. Jonathan Quist

    April 28, 2010 at 3:21 pm

    I wonder whether there are legal precedents supporting either side, regardless of the dental evidence?

    If the entirety of his life within the United States has been with one documented birth date, at what point does that become legally binding and irrevocable?

    For instance, if he had obtained a driver’s license, but is now declared to have been legally fifteen, is he then guilty of making fraudulent statements to the State of Minnesota? (Could the clearance on the murder charge automatically make him a felon on an unrelated but age-connected charge?)

    While I acknowledge that his defense team is doing their job, trying to clear their client, my gut reaction is that if Mahdi Ali has been living with a 1994 birthday for the past dozen years, then changing the date now that it’s convenient is somewhat disingenuous, at best.


    • D.P. Lyle, MD

      April 28, 2010 at 3:32 pm

      Are you saying that defendants and their attorneys might be dishonest? I’m shocked. A birth certificate is a document like a w ill or contract and as such its validity can be challenged in court. So even if he were born in the US and had an apparently legitimate certificate, this could still be challenged and could be found fraudulent. Or it could be upheld. If fraudulent then the police would need to determine who forged or altered the document–his parents at birth or him or someone he knew at the county courthouse where these are often maintained at a later date. Then the person who did it could face charges.


      • Jonathan Quist

        April 28, 2010 at 7:11 pm

        As shocking as the concept is, what I actually had in mind was that his original birth certificate was unavailable, or perhaps did not even exist, and the birth date documented in the U.S. was in error through innocent accident.

        In that situation, I would fault the attorneys if they didn’t try to use the error to their client’s benefit – that is their obligation. If the defendant had believed himself sixteen, though, does he really deserve a “do-over”?


      • D.P. Lyle, MD

        April 28, 2010 at 8:07 pm

        That would put him in a pickle. With no certificate it might be impossible to ascertain his true age and if he told authorities he was 16 then that might stand–or not. It would depend on how things went in the courtroom and how the judge reacted. Good scenario for fiction though.


  4. Jennifer Mercede

    June 25, 2010 at 3:04 pm

    I am wondering if it is certain that the forensic dentist is planning on using deciduous teeth as a proxy measure of age? Methods for aging individuals in forensic/physical anthropology and archaeology use the broad measures, such as, suture closure and dental eruption; but, there are more sensitive proxies as well. Dental cemetum has growth layers that can give a more refined estimate of age in animals. If there are standardized methods for humans to determine, for example, which tooth is the better measure (I am not aware of any, but I deal with non-humans), then is possible to use a pulled tooth and calculate age based on dental cementum annuli. These layers corresponds to age nicely in other mammals; it could be used on this young man, if he were willing to sacrifice a tooth.


    • Jonathan Quist

      June 26, 2010 at 11:17 am

      Are cementum annuli definitive in humans living in the modern, developed world?

      Wild animals, particularly in a region such as Minnesota with wide annual climate swings, are subject to seasonal changes in food supply, physical activity, etc.

      Relatively few present-day residents of the U.S. are subject to seasonal variations, though some are returning to local, seasonal produce.

      If diet is the primary factor in the formation of these annuli (my speculation, I don’t know this to be the case), then would there by anything significant to measure?


      • D.P. Lyle, MD

        June 26, 2010 at 3:39 pm

        It has been used in aging primates but as far as I know not humans…but I see no reason that it wouldn’t be of use to some degree.


    • Jennifer Mercede

      June 26, 2010 at 8:57 pm

      I did a not-very-exhaustive check of an old textbook (Byers, Forensic Anthropology, 2nd Ed.). Cementum is roughly deposited annually. However, your question made me think twice about my comment for two reasons. First, seasonal changes in growth rings are common for invertebrates who create skeletal structures from the surrounding environment; drawing upon calcium or argon, depending on the species. Second, looking this up confirmed that diet matters. The rate of deposition in modern humans is diet dependent, in that, deposition varies with the nutritional stress of the individual (and possibly sex and ancestry). Using cementum annuli might be valid if there were sex-specific studies done using people with known ages that were from the region the boy was from before coming to the U.S., but it would have to be done on deciduous teeth for reasons mentioned below.

      The author of said textbook states that, in general, this method is not used. The reasoning being that the more extensive process of calculating age by counting the annulations does not increase the accuracy of the estimate enough to justify it. Three factors contribute to this: 1) the variation mentioned before (nutrition, sex, region); 2) inter-analyst variation; and most importantly, 3) the annulations (in permanent teeth) are counted beginning from the average age at eruption for each tooth. Therefore, the methods the article is referring to, actually establish the starting assumptions that the dental cementum method uses.

      Even though my comments did not bring anything to bear on the content of the article, I can’t resist sharing the last thing I learned while researching this. There is another not-often used method for estimation of age (age at death usually), whereby a number of changes in teeth (attraction, secondary dentin deposition, changes in the paradentium, cementum apposition and root reabsorption/transparency) are ranked on a scale of 0-4, plugged into a formula, and put through multiple regression analysis. Interestingly, even this is not believed to repay investigators with more accurate estimates than those arrived at by looking at primary ossification centers and dental characteristics.

      There is probably an old adage that speaks to this. Simple = better, or some such thing.


      • Jonathan Quist

        June 27, 2010 at 9:09 pm

        >There is probably an old adage that speaks to this. Simple = better, or some such thing.

        I was an electrical engineering student in the late ’70’s/early ’80’s – a time when good scientific calculators had recently become affordable for most college students. One of my circuit design professors took the very practical approach that, since typical electronic component values are accurate within 10 percent (or 5, if you want to pay more), it was pointless to compute beyond 3 significant digits.

        He’d make up problems off the top of his head, not caring whether the answers were round numbers, and ask us for the answer. And he’d always chuckle at the flurry of key-pounding in the room, because he always had the answer first, usually a full minute before anyone else, working the math in his head. I came the closest to catching him – after my calculator broke, and I reverted to a slide rule. The extra digits, which were meaningless in the broader context, were costly in terms of effort and time.

        Then again, if I were up for a life sentence, I’d want the court to admit the more exhaustive test as evidence. If necessary, I could knock over a few convenience stores to pay for it after acquittal…


  5. Jonathan Hayes

    June 26, 2010 at 7:01 pm

    I’m pretty sure that transverse sections of teeth (as well as painstaking measurement and proportion calculations of the heights of different parts of the tooth) have been used to estimate age, but it’s only an estimate – anthropologists in particular are keen on the “range of ages” thing, which is wholly appropriate.

    Even if there were standards for estimating age by cement deposition, they’d be based on an American cohort, and would be effectively useless for estimating the age of a boy born and raised in Kenya under who-knows-what nutritional circumstances for a period of time before being moved to the US.

    Too many variables. As there will be, I think, with any anatomical approach to determining age to the demanded degree of precision.

    PS In my office right now, one of the big anthropologic research interests is using bone histology to determine age.



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