Fabrication of DGUs

A large number of criminal shootings are
"drive-bys" --- fired from long range and more likely to hit an
extremity than a self-defence shooting at close range. These factors
suggest that defensive shootings would be more lethal than criminal ones.

John Briggs writes:

Any data on the proportions of such long range shootings? I confess I have
not seen a serious treatment of the topic. News acounts leave one with the
impression that such shootings involve whole carloads of machinegun
equipped gangbangers. Our streets aren't that wide here in the US. We
aren't talking 100 yard firefights. Whether the extra few yards of range
offsets the more serious intent of the shooters I cannot say.

By long range I meant, of course, the width of the street.

There was a study of gunshot wounds treated in an inner-city hospital
published in J of Trauma a couple of years ago. They found that on
average shotgun wounds (mainly bird shot) were less serious than
handgun wounds. This suggests that they are not doing the shooting at
really close range.

The enormous difference between 800,000 (5 year recall, houshold DGUs)
and 2.5M (1 year recall, personal DGUs) is in fact string evidence
that there is some fabricating going on. Suppose you have made up a
DGU. Now Kleck asks you for details. "Was it within the past year?"
You answer randomly. So, you would expect about 50% of the fabricated
DGUs to occur in the past year. On the other hand, a real DGU would

Is that the order of the questioning? "Ever had a DGU? Past year? Past five

No, the first question asks if they had one within the last five
years. If they say yes, he asks if it was within the past year.

OK, assume that indeed half of the fabrications are reported in the
one-year data and half in the five-year. Assume all of the one-year
respondents are braggarts and subtract them plus an additional equal number
of presumed braggarts from the five-year positives you have a fair number
of presumably honest respondents left. What sort of DGU computation do you
get then?

About half a million.

be equally likely to fall into any of the five years and you would
expect about 20% to occur in the past year. In fact Kleck found 40%
said that it had occured in the past year, which suggests that there
is more fabricating than truth-telling going on. Because 40% is twice
20%, you get a factor of two difference in the estimate depending on

Perhaps we use the word "fabricating" differently. Honest telescoping would
not be fabricating to me. The incident occurred but is misreported as to
its exact time. Fabrication suggests knowing manufacture of a phoney event.
Can you really be sure that the 40% one-year figure strongly supports your

I am assuming that both forgetfulness and telescoping operate to provide a
net overall reporting error that distorts not only the overall total of
reported incidents but which is different at different points in the survey
period. Suppose 100 actual events each year. Honest telescoping leads
respondents to overstate actuals in thet first year by 20%. Each year
(before the first) 10% of events are honestly forgotten or supply the
"pool" out of which telescoped events get moved forward in time. This would
give 2nd through 5th year recollections of 90, 80, 70 and 60 events. This
would give 420 honestly if inaccurately reported events in the five year
period or 85 per annum while the one year reply rate would give 120, almost
50% higher.

But not 100% higher, which is what Kleck found.

Are such magnitudes of telescoping and forgetfulness unheard
of? That's a real question, not a rhetorical one.

I don't know.

Does he discount telescoping completely or is my understanding (as
exemplified in my 100 event example) wrong altogether?

He believes that telescoping and recall failure tend to cancel out, so
the 2.5M estimate does not include any correction for telescoping.

I am assuming that
net telescoping would be more likely to be pronounced in the first year and
that forgetfulness increases the farther back one tries to remember. Later,
you mention that Kleck "cites some data that suggests that telescoping
would make no more than a 20% difference" but I don't know exactly how the
difference is defined.

A 20% difference in the estimate.

In trying to resolve the discrepancies between Kleck and the NCVS regarding
to shoot) whereas Kleck's respondents include not only NCVS types but, say,
the female apartment dweller who refers to her handgun to send a persistent
stranger away from her door.

Kleck take pains to only count DGUs against actual crimes.

Did Kleck's interviewers go into the
same excruciating detail as the NCVS interviewers? The NCVS intentionally
tries to elicit false positives by asking respondents to report incidents
even if they weren't sure a crime had been committed and then tries to weed
these out. I am sure Kleck tried to screen out nervous people going to
investigate tree branches scraping against windows but I had not thought
his survey was as detailed as the NCVS regarding the crime victimization.

Not as detailed, but he only counted those cases where the respondent
identified a particular crime that was being attempted.

The top of the NCVS range for B seems rather high, but 30% seems like
reasonable number for B. Kleck's survey gives numbers for B that are
way too low.

But the reasonableness of the 30% figure lies (only?) in the fact that it
is between the police 37% and the criminal 18%, yes? And the
unreasonableness of Kleck's 2% to 5% derives (only?) from the fact that it
is so much lower than the criminals' 18%, yes? Actually, it derives partly

because he felt forgetfulness was more of a problem than telescoping. Does
the final published version note the lower five-year estimate?

Afraid not. The lowest estimate he has is 1.2M, and it's clear that he
regards the 2.5M one as best.

Well, I'll talk to him about that. (The 1.2 million is his five-year
estimate or a lowest one-year limit?)

Five year estimate.

In any event, your calculation should prompt us to wonder how civilian DGUs
ought to compare with police and criminal "success" rates. If the

For example, a police officer is under a duty to stay engaged with a

Civilian DGUs ought to involve fewer shots, on average.

Not necessarily... The attacker is probably more motivated to attack
his victim than to fight third parties (like police).

(This would suggest criminal attacks are unusually deadly in intent.

Only as compared to criminal attacks on police when they intervene.

While I'm here, this is my estimate of the number of DGU-related

The NEISS estimates 60k Assault/legal intervention nonfatal firearm
injuries treated in hospitals. According to the NCVS about 90% of
those wounded in this way get hospital treatment, so there are roughly
70k such woundings each year. Add in 18k deaths and I estimate about
90k assault/legal intervention shootings altogether. Using the data
from Table 4.2 (on Civilian Legal Defensive Homicides) as Kleck does,
about 10-13% of the woundings will be self-defence, or 9k-12k, i.e
roughly 10,000.

If I read NCJ-147003 correctly it states that in 1992 offenders armed with
handguns committed a 931,000 violent crimes I assume NCVS, not UCR,
figure). The report gives the following shooting/hit rates based on 1987-1992:

 Shot at victim         16.6%
 Hit victim              3.0
 Missed victim          13.6

Three per cent of 931,000 is 27,930. If 90% of these incidents send the
victim to the hospital that accounts for 25,137 nonfatal firearms injuries
treated in hospitals. If another 10,000 are civilian legal defensive
woundings (which assumes all injured criminals go to the hospital--a matter
in dispute) we account for only half of your 70,000 figure: who is taking
up the other hospital beds?

70,000 is my estimate of the total woundings. The number treated in
hospital is 60,000.

The NCVS is known to undercount gunshot wounds by a factor of two.
Cook believes that the discrepency is caused because many of these
victims are criminals who would not agree to participate in NCVS.
This is why I believe that the NCVS could undercount DGUs by as much
as a factor of two. As well as the 80,000 DGUs that the NCVS
detects, there could be another 80,000 by criminals defending against
other criminals.


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