Dear Colleagues,
The archives do not seem to have the summary of replies to my question about
baby shaking (which I sent two years ago, maybe to the wrong destination).
Anyway, here is the summary again. The replies were very valuable to those
defending the case in Alameda County, California. I will post another

Dear Biomechanicers,
Thank you all who responded to my request for help
about a baby-shaking case. A summary follows.
This case is ongoing, and I intend to post
any more information that I think will
be of general interest.

Derek Hendry.

"I have a "baby-shaking" case. The prosecution is
going to say that the baby was in my client's care when the baby stopped
breathing (true). At the hospital, the red blood cell count was decreasing,
showing that the system had not yet stabilized, showing,
in turn, that the injury was "recent." An expert witness is going
to say that brain swelling was continuing when the baby was examined in the
hospital. The baby had no external injuries.

"The prosecution is going to use these facts and testimony to conclude
that the baby was shaken by my client. I have strong reasons to
believe that the baby was NOT shaken by my client.

"I want to understand the biomechanics and physiology of intracranial
Some important questions relate to the time course
of the symptoms of brain damage.
Other important questions relate to the effects of various kinds
of mechanical insult. What is the danger threshold of acceleration
of the head? What physical events produce dangerous levels
of head acceleration?

"My client, myself, and my colleagues will appreciate information, data,
and leads.

" I will post a synopsis of all helpful replies.


Date: 94-06-09 04:25:08 EDT

Dear Derek,

I read your message with respect to "baby-shaking". I must say I
have never heard of this before (apart from a custom in this part
of the Netherlands where the neigbours come by to shake a newborn
kid; gently that is). From your message I conclude the baby you
mentioned has had brain damage and that the suspicion is someone
has caused this brain damage by violently shaking the baby.
Personally I find it highly unlikely that manually shaking a baby
can induce brain damage. I have several reasons for this.

With respect to manually exerting the acceleration force :
I am sure measurements have been done to determine accelarations
which the adult brain can stand. The area to look would be
aeronautical engineering. I know that pilots of high performance
aircraft can stand up to 5g without blacking out, and I think at
least up to 9g while blacking out but recovering immediately as
soon as the accelerations have decreased again. This means 9-10g
is not yet the limit where brain damage would occur. I suppose the
young growing brain of a baby can not take as much. Still, accelerating
to 10g a mass of, say 4 kilograms, would require a force of 400 Newton.
To give you an idea : benchpressing a 90-lb weight.

With respect to accelerating the head :
Sorry this sounds somewhat technical/mechanical; I am aware of
the fact babies are not merely masses or objects.
Suppose somebody is shaking a baby. He or she will hold the body,
presumably under the armpits, but not the head. Also, the baby
would be held out forward. The range of movement is hereby
restricted because of the limited arm length. Because babies do
not have strong neck musculature, the head will not follow the
exact movements of the body. Mechanically : The body-neck-head can
for this purpose be considered as a system consisting of a large
mass, to which a small mass is connected by a spring-damper. If
the large mass is accelerated, the small mass will generally not
undergo the same acceleration as the large mass. Theoretically it
is possible to bring the small mass into resonance which could
raise the level of acceleration to a value above the acceleration
of the small mass. In the case of the baby, this would in my
opinion require deliberate "careful" action, if it is possible
at all.

Limitation of the forces which can be delivered to the head :
As mentioned above, the neck musculature of babies is not very
well developed yet. This means the head is supported mainly by
passive structures (vertebrae and ligaments). Anybody who has
ever held a small baby knows the head must be supported in order
to protect the neck. As far as I know there have been cases of
young children who have been put in a bicycle-seat before their
necks were strong enough, which caused neck lesion when the cycle
hit a hole in the pavement. The point is this. Suppose that
a baby is shaken vigorously enough to induce accelerations which
would cause brain damage. In my opinion the neck would break long
before actual brain damage could ever occur. The pilots flying the
aircraft I mentioned before do not break their neck because their
musculature is better developed, and sideways support of their
head is provided so that the neck is not loaded in transverse

Of course the matter is changed completely if the head would be
struck by or against another object. The accelerations occurring
in this case would be much higher than by "just" shaking. I
assume that evidence of impact would normally have to be present
in this case though. Absence if this kind of evidence would
at least require deliberate action of molesting and hiding the
evidence (use of sandbags or the like).

I hope some of this may be useful to you.

Yours sincerely,

Edsko Hekman
Twente University
Fac. Werktuigbouwkunde - BW
Postbus 217Date: 94-06-08 23:19:56 EDT
7500AE Enschede
The Netherlands

Date: 94-06-09 03:06:25 EDT
Subj: Baby-shaking
To: Dhendry

Hi Derek,

Re your Biomch-L posting about baby shaking, have you talked to
Werner Goldsmith in the mechanical engrg dept at Berkeley? He is
an expert on head injuries due to impact, so he should have data
on accelerations and injuries.

Best regards,
Date: 94-06-09 07:33:06 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

I think someone at University of Strathclyde, Scotland was working on this
about 10 years ago, with reference to potential damage to babies from
putting them in those baby-bouncers hanging from doorways - don't know any
more details but might be a useful lead.

David Pickles
Date: 94-06-09 08:39:35 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

What are your strong reasons for believing that your client did not shake
the baby?
Date: 94-06-09 10:15:51 EDT
Subj: Biomechanics of Baby-shaking
To: Dhendry

This has to be a very important issue to try to resolve. I would
contact Professor Donald Huelke at the University of Michigan Transportation
Research Institute (313) 764-4367 to see if he has any good leads for you.
He has considerable experience in impact and whiplash injuries and may
know of a good neurologist. I presume you are familiar with the HIC,
but I don't know whether it has been validated in the pediatric population.
Date: 94-06-09 09:23:00 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

Check with Al King at Wayne State. Al has been working with head injury in
auto accidents and has a great deal of experience in closed head injury.
-Good Luck,
Please let me know what you find out.
-Mark Redfern
University of Pittsburgh
Date: 94-06-09 15:39:40 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

There was a paper written by Thibault, Margulies, Duhaime and some
others, in Journal of Neurosurgery in 1984 which might be useful
to you. Sorry, I haven't got the exact reference, but the gist
was that a normal human being can't shake a baby hard enough to
cause diffuse axonal injury. You could look it up.

-Lynne Bilston

Date: 94-06-09 18:45:42 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

While acknowledging the seriousness of your case, I believe your
first step should be to inquire who on this list might be available
for hire as your expert witness.

Date: 94-06-09 19:05:06 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

Derek! I was acting as a consultant in the similar case of "baby - shaken"
syndrome. The literature search provide very limited amount of information
can used. From our research it is clear that the adult can shake the baby
which will result in fatality. However, one has carefully examine clinical
evidences of the pathology in order to come to definite conclusion. I hope
this is helpful. Sincerely.

*................................................. ........................*
* " There are no shortcuts to any place worth going....." *
* *
*================================================= ========================*
* Professor Arkady Voloshin *
* Department of Mechanical phone: 610-758-4118 *
* Engineering and Mechanics fax: 610-758-6224 *
* Lehigh University email: AV01@LEHIGH.EDU *
* 19 Memorial Drive West *
* Bethlehem, PA 18015 USA *

Date: 94-06-09 19:07:50 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

Dear Derek:
You have posed many serious questions regarding head injuries and head injury
mechanisms.. After studying head injuries and head protection for many years,
we still don't have solid answers to many of your questions. Given that you
are acting on behalf of your client, I would STRONGLY recommend that your
client retain the services of an expert in the area of head injury and head
injury mechanisms. There are many qualified people who do this kind of work
for a living and are quite adept at providing expert witness testimony.

I should also warn you that consulting with these people is not cheap.

In any event, if I haven't convinced you to obtain some outside expert
consulting, you may want to refer to Biomechanics of Head Injuries, edited by
Dr. Alan Nahum and Dr. John Melvin, 1992.

Good Luck,

Terry Smith
USC Head Protection Research Laboratory
Los Angeles, California

Date: 94-06-09 19:56:18 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

Dear Mr. Hendry,

I am intrigued with your Baby-shaking case. My name is Scott McClellan.
I have an MS in Bioengineering and am currently a doctoral candidate at
the University of Utah. I recently finished a project for the United
States Diving Foundation, a subsidiary of the United States Olympic
Committee which was directly involved with the human limits and tolerances
for head (brain) injury. I was asked to determine the biomechanics of head
injury for platform impacts and provide them with a research protocol to
increase safety and reduce the risk for serious head injury.

Most of my experience has been in the analysis of head impacts. While your
case does not require "impact" analysis, acceleration is still acceleration
independent of its source. There are several standard curves
used in industry as thresholds for survivable and or serious head injury
due to high accelerations and short impulse durations. Several of these are:

HIC Head Injury Criterion
WST Wayne State Tolerance Curve
BPT Brain Pressure Tolerance Curve
MSC Maximum Strain Criterion

It may be possible to determine the maximum accelerations a child could
sustain under shaking by a normal adult person and apply these values to
the established head injury curves to reach conclusions about the severity
or probability of shaking. However, small children and infants have
unique cranial characteristics which differ significantly from adult
humans other than size and mass. Some potential differences are stiffness
of the cranial suture joints, meninges development and attachment (which
can change brain shear), as well as general neck muscle laxity. All of
these variables will effect the potential cerebral acceleration magnitude
and should be considered.

Since I do not have any specific facts from your case I will refrain from
speculating. If you are interested in discussing the matter further I can
be reached at:

Date: 94-06-10 08:08:43 EDT
Subj: Re: Biomechanics of Baby-shaking
To: Dhendry

> Other important questions relate to the effects of variouskinds
> of mechanical insult. What is the danger threshold of acceleration
> of the head? What physical events produce dangerous levels
> of head acceleration?

You could try Mailing, Mr. Chris Snook is an
engineer who, in collaboration with others, has done a significant amount
of testing using human head models to determine impact magnitudes to
falling heads. This was done for playground surfaces, in relation to
legalities of head injuries and for car impacts. He has a knowledge of
the likely accelerations etc, that the head is subjected to and is trying
to associate this knowledge with a data base of car/pedestrian impacts.

The general model used in such trauma modelling is a function of both time
and acceleration imparted. That is, the amount of trauma potential is
normally represented by a function incorporating time and is therefore an
integral or a numerical integral of data. High acceleration, if imparted
for short periods of time, does not cause significant injury, whereas a
lower acceleration over a period of time may well cause trauma.