May 22, 2013
A few months ago I was thinking about that crack in the windshield of the Saturn. I looked around on FindMauraMurray.com, Topix and other places to get a sense for what people were thinking. The following summaries represent two common views:
 The damage to the Saturn, including the cracked windshield, is evidence of a prior crash and perhaps an indication that the car was being towed prior to the accident on 112. Related to this, Maura's head could not have hit that particular spot near the upper corner of the driver's side windshield in what probably was a fairly low speed impact, given the obstacle of the steering wheel and the deployment of the airbag.
 The crack is evidence that Maura suffered a head injury and thus might have been susceptible to collapsing not far outside the short distances away searched by authorities that night. The Murrays, for instance, appear to feel this way.
This is a picture of the crack in the window (with red lines highlighting it that have been added to the picture) on MauraMurrayMissing.com.
Bear in mind two caveats about this picture. First, it was taken some unknown time after the accident and so the cracks - according to an auto body guy I know - could have spread out a little more as temperatures changed and wind or rain influenced the the windshield. Second, whomever colored the crack's seams in the photo - to make them easier to see - had the ability, if they chose, to exaggerate or modify their appearance and thus the suggestive impact of the photo. I have no reason to think this happened mind you, and I don't allege that it did. Instead, simply in terms of prudently taking a neutral posture toward evidence, it is worth keeping in mind.
For what it is worth, the MauraMurrayMissing.com site states that the impact came from inside the car. I myself cannot tell by looking at the picture.
For purposes of this post, I provide the photo for a limited and specific purpose: to show the general location the crack.
It appears that a first, I subscribed to an intuitive idea that is not true. At first, I agreed with those who said her head never could above the steering wheel with enough velocity and energy to break the windshield. But then I started thinking about suddenly being thrown forward at 35 miles an hour (assuming the car stopped short) and I was not so sure. I talked it over with a engineer friend who has studied car-body crash dynamics. He said it as possible. He suggested that I watch some crash test dummy videos and think about how an airbag influences the vectors of force on the driver relative to the car in a crash.
So I did. Check out this video, for example.
While not proving anything about Maura's case, it debunks the facial validity (see yesterday's update to the "My Sister" post) around the concept that her head could not have gotten up into that corner of the compartment under the windshield in a relatively slow speed impact.
While a different car, the video shows a fairly low impact speed (25 miles an hour) with a air bag deployment. Look closely at the passenger compartment zoom in the slow motion replays. Look where the head gets thrown: upward, above the steering wheel. This is net influence on the body (the driver) of two forces: being thrown forward relative to the suddenly stopped car and the generally opposing force of the airbag in deployment.
In that context, consider too the possibility that Maura was drinking and perhaps intoxicated. If so, she may not have braced for impact in any way, even by tensing her body. Thus her body was even more likely to move a crash dummy's would. But even aside from that, there is so little reaction time in a stopped short accident, and the forces are so strong, that even bracing likely would not have made a difference in terms of where her body and head were thrown.
Finally, I noticed in this video a kind of secondary upward thrust of the head toward the upper windshield. This suggests the possibility of an injury to the back of Maura's head. That would tend to affect vision and spatial reasoning (i.e., perhaps making her more prone to getting confused and lost, as well as less able judge distances and dodge oncoming cars). Moreover, the onset of symptoms from head trauma is sometimes not immediate. Symptoms can manifest minutes, hours, or even days later, sometimes suddenly, sometimes gradually.
Call to action: if you know auto crash dynamics, or you are an engineer, or you have some other type of insight or expertise, I am really to interested to hear what people think. I am willing to bet that someone in our group knows this topic well and I could use their information to post an update and put a finer point on this topic.