THAT WAS THE KEY finding of the congressional investigation
that concluded
22 years ago that President John F. Kennedy,s murder in Dallas
in 1963 was
"probably ... the result of a conspiracy. A shot from the
grassy knoll
meant that two gunmen must have fired at the president within
a
split-second sequence. Lee Harvey Oswald, accused of firing three
shots at
Kennedy from a perch at the Texas School Book Depository, could
not have
been in two places at once.
A special panel of the National
Academy of Sciences subsequently
disputed the evidence of a fourth shot, contained on a police
dictabelt of
the sounds in Dealey Plaza that day. The panel insisted it was
simply
random noise, perhaps static, recorded about a minute after the
shooting
while Kennedy,s motorcade was en route to Parkland Hospital.
A new, peer-reviewed article in
Science and Justice, a quarterly
publication of Britain,s Forensic Science Society, says the NAS
panel,s
study was seriously flawed. It says the panel failed to take
into account
the words of a Dallas patrolman that show the gunshot-like noises
occurred
"at the exact instant that John F. Kennedy was assassinated.
In fact, the author of the article,
D.B. Thomas, a government
scientist and JFK assassination researcher, said it was more
than 96
percent certain that there was a shot from the grassy knoll to
the right
of the president,s limousine, in addition to the three shots
from a book
depository window above and behind the president,s limousine.
HOUSE INVESTIGATOR SEES VINDICATION
G. Robert Blakey, former chief
counsel to the House Assassinations
Committee, said the NAS panel,s study always bothered him because
it
dismissed all four putative shots as random noise even though
the three
soundbursts from the book depository matched up precisely with
film of the
assassination and other evidence such as the echo patterns in
Dealey Plaza
and the speed of Kennedy,s motorcade.
"This is an honest, careful scientific examination of
everything we did,
with all the appropriate statistical checks, Blakey said of Thomas,s
work.
"It shows that we made mistakes,
too, but minor mistakes. The main
thing is when push comes to shove, he increased the degree of
confidence
that the shot from the grassy knoll was real, not static. We
thought there
was a 95 percent chance it was a shot. He puts it at 96.3 percent.
Either
way, that,s beyond a reasonable doubt.,
The sounds of assassination were
recorded at Dallas police
headquarters when a motorcycle patrolman inadvertently left his
microphone
switch in the "on position, deluging his transmitting channel
with what
seemed to be motorcycle noise. Using sophisticated techniques,
a team of
scientists enlisted by the House committee filtered out the noise
and came
up with "audible events within a 10-second time frame that
it believed
might be gunfire.
The Warren Commission had concluded
in 1964 that only three shots,
all from behind, all from Oswald,s rifle, were fired in Dealey
Plaza as
the motorcade passed through. But the House experts, after extensive
tests, found 10 echo patterns that matched sounds emanating from
the
grassy knoll, traveling carefully measured distances to nearby
buildings
and then bouncing off them to hit the open motorcycle transmitter.
They also placed the unknown gunman
behind a picket fence at the
top of the grassy knoll, in front of and to the right of the
presidential
limousine. The House committee concluded that this shot missed,
and that
Kennedy was killed by a final bullet from Oswald,s rifle. Thomas,
by
contrast, believes it was the shot from the knoll, seven-tenths
of a
second earlier, that killed the president.
MISALIGNED AUDIO CHANNELS
The NAS panel, assigned to conduct
further studies after the
committee closed down, said in 1982 that the noises on the tape
previously
identified as gunshots "were recorded about one minute after
the president
was shot.
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The NAS experts, headed by physicist
Norman F. Ramsey of Harvard,
reached that conclusion after studying the sounds on the two
radio
channels Dallas police were using that day. Routine transmissions
were
made on Channel One and recorded on a dictabelt at police headquarters.
An
auxiliary frequency, Channel Two, was dedicated to the president,s
motorcade and used primarily by Dallas Police Chief Jesse Curry;
its
transmissions were recorded on a separate Gray Audograph disc
machine.
The shooting took place within
an 18-second interval that began
with Curry in the lead car announcing on Channel Two that the
motorcade
was approaching a triple underpass and ended with the chief stating
urgently: "Go to the hospital. What seemed to be the gunshots
were picked
up on Channel One during that interval.
The NAS panel pointed out that
Dallas County Sheriff Bill Decker
could be heard on both channels saying, "... Hold everything
secure ...
seemingly about a half-second after the last gunshot on Channel
One. Curry
had already told everyone on Channel Two a minute earlier to
go to the
hospital. As a result, the Ramsey panel concluded that the supposed
gunshot noises came "too late to be attributed to assassination
shots.
What actually happened was that
Curry issued his "go to the
hospital order right after the first shots were fired, wounding
Kennedy
and Texas Gov. John Connally. The final bullet was fired in almost
the
same instant that Curry uttered his command. A minute later,
Decker,
riding in the same car with Curry, grabbed the mike and issued
his orders
to "hold everything secure.
SEVERAL ERRORS CITED
The study,s author said the chances that the National Academy
of Science,s
single-gunman theory was correct were 1 in 100,000.
The NAS experts made several errors, Thomas said, but their
biggest mistake was in using Decker,s words to line up the two
channels.
They ignored a much clearer instance of cross talk when Dallas
police Sgt.
S. Q. Bellah can be heard on both channels, asking: "You
want me to hold
this traffic on Stemmons until we find out something, or let
it go?
Those remarks come 179 seconds
after the last gunshot on Channel
One and 180 seconds after Curry,s order to "go to the hospital
on Channel
Two. When Bellah,s words are used to line up the two channels,
Thomas
found, the gunshot sounds "occur at the exact instant that
John F. Kennedy
was assassinated.
How is it, then, that Decker,s
remarks on Channel One come a full
minute after Curry,s on Channel Two and yet a half-second after
the last
gunshot on Channel One?
"It,s a misplaced bit of speech,
Thomas said in an interview. "An
overdub. The recording needle for Channel One probably jumped.
You can
hear Decker giving a whole set of instructions on Channel Two,
but on
Channel One, you get only a fragment, ... hold everything secure.
... ,
According to Thomas, the NAS panel
made other mistakes: in
calculating the position of the grassy knoll shooter, in fixing
the time
of that shot and in stating the Channel Two recorder had stopped
when it
hadn,t. In all, Thomas said, the chances of the NAS panel having
been
right were 1 in 100,000.
House committee experts James Barger,
Mark Weiss and Eric
Aschkenasy, have always held firm to their findings of a shot
from the
knoll. Similarly, Ramsey, as chairman of the NAS panel, said
last weekend
that he was "still fairly confident of his group,s work,
but he said he
wanted to study the Science and Justice article before making
further
comment. He said he did not recall the Bellah cross talk.
