(b) The Sense of Sight.
Section 37. (I) General Considerations.
Just as the sense of sight is the most dignified of all our senses, it
is also the most important in the criminal court, for most witnesses
testify as to what they have seen. If we compare sight with the
hearing, which is next in the order of importance, we discover the
well-known fact that what is seen is much more certain and trustworthy
than what is heard. "It is better to see once than to hear
ten times," says the universally-valid old maxim. No exposition,
no description, no complication which the data of other senses offer,
can present half as much as even a fleeting glance. Hence too, no
sense can offer us such surprises as the sense of sight. If I imagine
the thunder of Niagara, the voice of Lucca, the explosion of a
thousand cartridges, etc., or anything else that I have not heard,
my imagination is certainly incorrect, but it will differ from reality
only in degree. It is quite different with visual imagination. We
need not adduce examples of magnificence like the appearance of
the pyramids, a tropical light; of a famous work of art, a storm at
sea, etc. The most insignificant thing ever seen but variously
pictured in imagination will be greeted at first sight with the words:
"But I imagined it quite different!" Hence the tremendous importance
of every local and material characteristic which the criminal
court deals with. Every one of us knows how differently he has, as
a rule, imagined the place of the crime to be; how difficult it is
to arrive at an understanding with the witness concerning some
unseen, local characteristic, and how many mistakes false images of
the unseen have caused. Whenever I ciceroned anybody through
the Graz Criminal Museum, I was continually assailed with "Does
this or that look so? But I thought it looked quite different!"
And the things which evoke these exclamations are such as the
astonished visitors have spoken and written about hundreds of
times and often passed judgments upon. The same situation occurs
when witnesses narrate some observation. When the question
involves the sense of hearing some misunderstanding may be popularly
assumed. But the people know little of optical illusions and
false visual perceptions, though they are aware that incorrect auditions
are frequent matters of fact. Moreover, to the heard object
a large number of more or less certain precautionary judgments are
attached. If anybody, e. g., has
heard a shot,
stealthy footsteps,
crackling flames, we take his experience always to be
approximate.
We do not do so when he assures us he
has
seenthese things or
their causes. Then we take them—barring certain mistakes in
observation,—to be indubitable perceptions in which misunderstanding
is impossible.
In this, again, is the basis for the distrust with which we meet
testimony concerning hearsay. For we feel uncertain in the mere
absence of the person whose conversation is reported, since his
value can not be determined. But a part of the mistrust lies in the
fact that it is not vision but the perennially half-doubted hearing
that is in issue. Lies are assigned mainly to words; but there are
lies which are visual (deceptions, maskings, illusions, etc.). Visual
lies are, however, a diminishing minority in comparison with the lies
that are heard.
The certainty of the correctness of vision lies in its being tested
with the sense of touch,—i. e. in the adaptation of our bodily
sense to otherwise existing things. As Helmholtz says, "The agreement
between our visual perceptions and the external world, rests,
at least in the most important matters, on the same ground that all
our knowledge of the actual world rests on, upon the experience
and the lasting test of their correctness by means of experiments,
i. e., of the movements of our bodies." This would almost make it
seem that the supreme judge among the senses is the touch. But
that is not intended; we know well enough to what illusions we are
subject if we trust the sense of touch alone. At the same time we
must suppose that the question here is one of the nature of the body,
and this can be measured only by something similar, i.e., by our
own physical characteristics, but always under the control of some
other sense, especially the sense of sight.
The visual process itself consists, according to Fischer, "of a
compounded series of results which succeed each other with extraordinary
rapidity and are causally related. In this series the
following elements may principally be distinguished.
(1) The physico-chemical process.
(2) The physiologico-sensory.
(3) The psychological.
(4) The physiologico-motor.
(5) The process of perception."
It is not our task to examine the first four elements. In order
clearly to understand the variety of perception, we have to deal
with the last only. I once tried to explain this by means of the
phenomenon of instantaneous photographs (cinematographs). If
we examine one such representing an instant in some quick
movement, we will assert that we never could have perceived
it in the movement itself. This indicates that our vision is
slower than that of the photographic apparatus, and hence, that
we do not apprehend the smallest particular conditions, but that
we each time unconsciously compound a group of the smallest
conditions and construct in that way the so-called instantaneous
impressions. If we are to compound a great series of instantaneous
impressions in one galloping step, we must have condensed and
compounded a number of them in order to get the image that we
see with our eyes as instantaneous. We may therefore say that the
least instantaneous image we ever see with our eyes contains many
parts which only the photographic apparatus can grasp. Suppose
we call these particular instances a, b, c, d, e, f, g, h, i, j, k, l, m;
it is self-evident that the manner of their composition must vary
with each individual. One man may compound his elements in
groups of three: a, b, c,—d, e, f,—g, h, i, etc.; another may proceed
in dyads: a, b,—c, d,—e, f,—g, h,—etc.; a third may have seen
an unobservable instant later, but constructs his image like the first
man: b, c, d,—l, m, n, etc.; a fourth works slowly and rather inaccurately,
getting: a, c, d,—f, h, i,—etc. Such variations multiply,
and when various observers of the same event describe it
they do it according to their different characteristics. And the
differences may be tremendous. Substitute numerals for letters and
the thing becomes clear. The relative slowness of our apprehension
of visual elements has the other consequence that we interpolate
objects in the lacunæ of vision
according to our
expectations. The best
example of this sort of thing would be the perception of assault and
battery. When ten people in an inn see how A raises a beer glass
against B's head, five expect: "Now he'll pound him," and five
others: "Now he'll throw it." If the glass has reached B's head
none of the ten observers have seen how it reached there, but the
first five take their oath that A pounded B with the glass, and the
other five that he threw it at B's head. And all ten have really
seen it, so firmly are they convinced of the correctness of their swift
judgment of expectation. Now, before we treat the witness to
some reproach like untruth, inattention, silliness, or something
equally nice,
we had better consider whether his
story is not true,
and whether the difficulty might not really lie in the imperfection
of our own sensory processes. This involves partly what Liebmann
has called "anthropocentric vision," i. e., seeing with man as the
center of things. Liebmann further asserts, "that we see things
only in perspective sizes, i. e., only from an angle of vision varying
with their approach, withdrawal and change of position, but in no
sense as definite cubical, linear, or surface sizes. The apparent size
of an object we call an angle of vision at a certain distance. But,
what indeed is the different, true size? We know only relations of
magnitude." This description is important when we are dealing
with testimony concerning size. It seems obvious that each witness
who speaks of size is to be asked whence he had observed it,
but at the same time a great many unexpected errors occur, especially
when what is involved is the determination of the size of
an object in the same plane. One need only to recall the meeting
of railway tracks, streets, alleys, etc., and to remember how different
in size, according to the point of view of the witness, various objects
in such places must appear. Everybody knows that distant things
seem smaller than near ones, but almost nobody knows what the
difference amounts to. For examples see Lotze, "Medical Psychology,"
Leipzig, 1852.
In addition we often think that the clearness of an object represents
its distance and suppose that the first alone determines the
latter. But the distinctness of objects, i. e., the perceptibility of a
light-impression, depends also upon the absolute brightness and the
differences in brightness. The latter is more important than is
supposed. Try to determine how far away you can see a key-hole
when the wall containing the door is in the shadow, and when there
is a window opposite the key-hole. A dark object of the size of a
key-hole will not be visible at one hundredth of the distance at which
the key-hole is perceived. Moreover, the difference in intensity
is not alone in consideration; the intensity of the
object with regard
to its background has yet to be considered. Aubert has shown that
the accuracy of the distinction is the same when a square of white
paper is looked at from an angle of 18", and when conversely a
square of black paper on white background is looked at from an
angle of 85". "When we put a gray paper in the sunshine, it may
become objectively brighter than white paper in shadow. But this
does not prevent us from knowing one as gray and the other as
pure white. We separate the color of the object from the intensity
of the incident light." But this is not always so simple, inasmuch as
we know in the case in hand which paper is gray and which white,
which is in the sunlight and which in the shadow. But if these facts
are not known mistakes often occur so that a man dressed in dark
clothes but in full light will be described as wearing lighter clothes
than one who wears light clothes in the shadow.
Differences of illumination reveal a number of phenomena difficult
to explain. Fechner calls attention to the appearance of stars:
"At night everybody sees the stars, in daylight not even Sirius or
Jupiter is seen. Yet the absolute difference between those places
in the heavens where the stars are and the environing places is just
as great as in the night—there is only an increase in illumination."
Of still greater importance to us is the circumstance noted but not
explained by Bernstein. If, in daylight, we look into a basement
room from outside, we can perceive nothing, almost; everything is
dark, even the windows appear black. But in the evening, if the
room is ever so slightly illuminated, and we look into it from outside,
we can see even small articles distinctly. Yet there was much
intenser light in the room in question during the day than the single
illumination of the night could have provided. Hence, it is asserted,
the difference in this case is a standard one. In open day the eye
is accustomed to the dominating brightness of daylight, beside
which the subdued illumination of the room seems relatively dark.
But in the evening one is in the dark, and hence even the little
light of a single candle is enough to enable one to see. That this
explanation is untrue is shown by the fact that the phenomenon is
not regulated even when the circumstances in question are made
identical. If, for example, you approach the window in daylight
with your eyes shut, lean your forehead against the pane and
shut out the light on the sides with your hands, and then open your
eyes, you see as little in the room as when you looked into it without
performing this ceremony. So again, if during the night you gazed
at some near-by gas lamp and then glanced into the room, there
is only a few moments' indistinctness at most, after that the single
candle is enough. The reason, then, must be different from the
assigned one—but whatever it is, we need only to maintain that
immediate judgment concerning numerous cases involving situations
of this kind would be overhasty. It is often said that a witness
was able to see this or that under such and such illumination, or
that he was unable to see it, although he denies his ability or inability.
The only solution of such contradictions is an experiment.
The attempt must be made either by the judge or some reliable
third person, to discover whether, under the same conditions of
illumination, anything could be seen at the place in question or not.
As to what may be seen in the distance,
experiment again, is the
best judge. The human eye is so very different in each man that
even the acute examination into what is known of the visual image
of the Pleiades shows that the average visual
capacity of classic
periods is no different from our own, but still that there was great
variety in visual capacity. What enormous visual power is attributed
to half-civilized and barbarous peoples, especially Indians, Esquimos,
etc.! Likewise among our own people there are hunters,
mountain guides, etc., who can see so clearly in the distance that
mere stories about it might be fables. In the Bosnian campaign of
1878 we had a soldier who in numerous cases of our great need to
know the enemy's position in the distance could distinguish it with
greater accuracy than we with our good field-glasses. He was the
son of a coal-miner in the Styrian mountains, and rather a fool.
Incidentally it may be added that he had an incredible, almost animal
power of orientation.
As we know little concerning far-sightedness, so also we are
unable to define what near-sighted people can see. Inasmuch as
their vision does not carry, they are compelled to make intellectual
supplementations. They observe the form, action, and clothes of
people more accurately than sharp-eyed persons, and hence recognize
acquaintances at a greater distance than the latter. Therefore,
before an assertion of a short-sighted man is doubted an experiment
should be made, or at least another trustworthy short-sighted person
should be asked for his opinion.
The background of objects, their movement and form have decided
effects on the difference in visual perception. It is an ancient
observation that lengthy objects like poles, wires, etc., are visible
at incomparably greater distances than, e. g., squares of the same
length. In examination it has been shown that the boundary of
accurate perception can hardly be determined. I know a place
where under favorable illumination taut, white and very thin telephone
wires may be seen at a distance of more than a kilometer.
And this demands a very small angle of vision.
Humboldt calls attention to the large number of "optical fables."
He assures us that it is certainly untrue that the stars may be seen
in daylight from a deep well, from mines, or high mountains, although
this has been repeatedly affirmed since Aristotle.
The explanation of our power to see very thin, long objects at
a very great distance, is not our affair, but is of importance because
it serves to explain a number of similar phenomena spoken of by
witnesses. We have either incorrectly to deny things we do not
understand, or we have to accept a good deal that is deniable. We
will start, therefore, with the well-known fact that a point seen for
a considerable time may easily disappear from perception. This
has been studied by Helmholtz and others, and he has shown how
difficult it is to keep a point within the field of vision for only ten
or twenty minutes. Aubert examines older studies of the matter
and concludes that this disappearance or confusion of an object is
peripheral, but that fixation of a small object is always difficult.
If we fix a distant point it is disappearing at every instant so that an
accurate perception is not possible; if however we fix upon a long,
thin body, e. g., a wire, it is unnecessary to fix a single point and we
may see the object with a wandering eye, hence more clearly.
Helmholtz adds that weakly objective images disappear like a
wet spot on warm tin, at the moment a single point is fixed, as does
e. g., a landscape seen at night. This last acute observation is the
basis of many a testimony concerning the sudden disappearance of
an object at night. It has helped me in many an examination, and
always to advantage.
In this connection the over-estimation of the moon's illuminating
power is not to be forgotten. According to Helmholtz the power of
the full moon is not more than that of a candle twelve feet away. And
how much people claim to have seen by moonlight! Dr.
Vincent[1]
says that a man may be recognized during the first quarter at from
two to six meters, at full moon at from seven to ten meters, and
at the brightest full moon, an intimate may be recognized at from
fifteen to sixteen meters. This is approximately correct and indicates
how much moonlight is over-estimated.
In addition to the natural differences of sight there are also those
artificially created. How much we may help ourselves by skilful
distinctions, we can recognize in the well-known and
frequently-mentioned business of reading a confused handwriting. We aim to
weaken our sense-perception in favor of our imagination, i. e. so
to reduce the clearness of the former as to be able to test upon it
in some degree a larger number of images. We hold the MS. away
from us, look at it askant, with contracted eyebrows, in different
lights, and finally we read it. Again, the converse occurs. If we
have seen something with a magnifying glass we later recognize
details without its help. Definite conditions may bring to light
very great distinctions. A body close to the face or in the middle
distance looks different according as one eye or both be used in
examining it. This is an old story and explains the queer descriptions
we receive of such objects as weapons and the like, which were
suddenly held before the face of the deponent. In cases of murderous
assault it is certain that most uncanny stories are told, later
explained by fear or total confusion or intentional dishonesty, but
really to be explained by nothing more than actual optical processes.
I do not believe that binocular vision is of much importance in
the law; I know of no case in ordinary vision where it matters whether
one or both eyes have been used. It is correct to assert that one side
or the other of a vertically held hand will be clearer if, before looking
at it with both eyes, you look at it with one or the other, but this
makes little difference to our purpose. It must be maintained that
a part of what we see is seen with one eye only,—if, e. g., I look at the
sky and cover one eye with my hand, a certain portion of the heaven
disappears, but I observe no alteration in the remaining portion.
When I cover the other eye, other stars disappear. Therefore, in
binocular vision certain things are seen with one eye only. This
may be of importance when an effect has been observed first with
both eyes, then with one; raising the question of the difference in
observation—but such a question is rare.
There are two additional things to consider. The first is the problem
of the influence of custom on increasing visual power in darkness.
This power is as a rule undervalued. No animal, naturally,
can see anything in complete darkness. But it is almost unbelievable
how much can be seen with a very little light. Here again, prisoners
tell numerous stories concerning their vision in subterranean
prisons. One saw so well as to be able to throw seven needles about
the cell and then to find them again. Another, the naturalist
Quatre-mére-Disjonval, was able so accurately to observe the spiders in
his cell as to make the observation the basis for his
famous "Aranéologie."
Aubert tells of his having had to stay in a room so dark as
to make it necessary for others to feel their way, but nevertheless
being able to read books without detection because the others could
not see the books.
How quickly we get used to darkness and how much more we
see after a while, is well known. It is also certain that the longer
you are in darkness the more you see. You see more at the end of a
day than after a few hours, and at the end of a year, still more. The
eye, perhaps, changes in some degree for just this purpose. But a
prolonged use of the visual mechanism tends to hypertrophy—
or atrophy, as the eyes of deep-sea fishes show. It is well, in any
event, to be careful about contradicting the testimonies of patients
who have long lived in the dark, concerning what they have seen.
The power to see in the dark is so various that without examination,
much injustice may be done. Some people see almost nothing at
twilight, others see at night as well as cats. And in court these
differences must be established and experimentally verified.
The second important element is the innervation of the muscles
in consequence of movement merely seen. So Stricker points out,
that the sight of a man carrying a heavy load made him feel tension
in the muscles involved, and again, when he saw soldiers exercising,
he almost was compelled openly to act as they. In every case the
muscular innervation followed the visual stimulus.
This may sound improbable but, nevertheless, everybody to
some degree does the identical things. And at law the fact may
be of importance in cases of assault and battery. Since I learned
it, I have repeatedly observed in such cases, from harmless assault
to murder, that people, although they had not been seen to deal
any blows, were often accused of complicity simply because they
were making suspicious movements that led to the following inference:
"They stuck their hands into their trousers pocket looking
for a knife, clenched their fists, looked as if they were about to
jump, swung their hands." In many such cases it appeared that
the suspects were harmless spectators who were simply more obvious
in their innervation of the muscles involved in the assault they
were eagerly witnessing. This fact should be well kept in mind;
it may relieve many an innocent.
[[ id="n37.1"]]
Vincent: Traité de Médecine légale de Légrand
du Saule.