Advancing Understanding, and Informing Prevention of 

Public Mass Shootings: Findings from NIJ Funded Studies – 

Part 1 

November 17, 2020 

The webinar will begin shortly. 
 

 

 

 

Presentations

Presentation Title 

Trends and Contagion in Mass Public 

Shootings 

Forecasting the Severity of Mass Public 

Shootings 

The Effect of State Gun Laws on Mass Public 

Shootings; and Exploring Averted Incidents 

Presenter 

James Alan Fox, Ph.D., Northeastern 

University 

Grant Duwe, Ph.D., Minnesota Department 

of Corrections 

Michael Rocque, Ph.D., Bates College 

Disclosure: This project is supported by Award No. 2018-75-CX-0025, awarded by the National Institute of Justice, Office of Justice Programs, U.S. 

Department of Justice. The opinions, findings, and conclusions or recommendations expressed in these presentations and during this webinar are those 

of the authors/presenters and do not necessarily reflect those of the U.S. Department of Justice. 
Trends and Contagion in Mass Public Shootings 

James Alan Fox 

Northeastern University 

NIJ Webinar 

November 2020 
 

 

 

 

Littler interest until 2012 trio of mass shootings 

NEW YORK (AP) — The horrific massacre of 26 

children and staff at a Connecticut elementary school, 

along with other mass shootings, was the top news 

story of 2012, narrowly edging out the U.S. election, 

according to The Associated Press' annual poll of U.S. 

editors and news directors 
Heightened scholarly interest 

Scholarly publications on mass shooting, 1980-2019 

12,000 

10,000 

ons 

8,000 

Publicati

6,000 

4,000 

2,000 

0 

22 

1980-84 

48 

1985-89 

109 

1990-94 

324 

1995-99 2000-04 2005-09 2010-14 2015-19 

Source: Google Scholar Years 

623 1,170 

2,930 

10,100 
Then came the data 

Source Definition of Mass Shooting Incident Years 

Included 

Incident 

Total 

Victims 

Fatally 

Shot 

Average 

Victims per 

Incident 

Fox/Duwe/Rocque 4+ victims killed by gunfire in public within a 24-hour 

period excluding felony-related incidents 1976-2019 164 1,164 7.1 

Peterson/Densley 4+ victims killed by gunfire in public 1966-2019 172 1,210 7.0 

Turanovic/Pratt 4+ victims killed by gunfire in a 24-hour period 1976-2019 808 4,035 5.0 

AP/USA Today/NUa 4+ victims killed by gunfire 2006-2019 326 1,783 5.5 

The Washington Post 4+ victims killed by gunfire in public excluding 

felony-related incidents 1966-2019 174 1,237 7.1 

Everytown for Gun Safety 4+ victims killed by gunfire 2009-2019 236 1,337 5.7 

Mother Jones 4+ victims (3+ since 2013) killed by gunfire in public 

excluding domestic and felony related incidents 1982-2019 118 948b 8.0 

Gun Violence Archive 4+ victims killed or injured by gunfire 2013-2019 2,345 2,651c 1.1 

a

 The AP/USA TODAY/Northeastern University database also track mass killings by means other than gunfire 

b The fatality counts in the Mother Jones databse frequently (but not always) include offender deaths 

c

 The fatality counts in the Gun Violence Archive include offender deaths 
 

 

 

Defining characteristics 

• Why mass public shootings with 4+ victim fatalities?

• What kind of event does the public tend to associate with the term

“mass shootings”?

• What frightens Americans? The more common or the more deadly?

What is a mass shooting? 

#Incidents Average 

Meaning of "mass shooting" Source 2013-19 #Fatalities 

4+ victims shot GVA 4345 1.1* 

4+ victims fatally shot AP/USAT/NU 183 5.7 

4+ victims fatally shot in public FDR 40 10.0 

*GVA includes assailant deaths in its fatality count
 

 

 

A minority of cases, but the most frightening 

• Mass public shootings are more deadly and often indiscriminate

• Can happen at any place, at any time, to anyone

Trends in Mass Shoootings by Type 

Source: Associated Press/USA Today/Northeastern Univ. Project 

20 

Family (44%) 

Felony (18%) 

Public (23%) 

Other/Unk. (15%) 

2006 2007 2008 2009 2010 

*2020 projection as of 11/5

2011 2012 2013 2014 

Year 

2015 2016 2017 2018 2019 2020* 

0 

5 

10 

15 

Incidents 
 

 

Trends in MPS incidence 

• Modest increase in cases from mid-2000s to mid-2010s

• A clear spike in 2018-19

Incidents 

Mass public shootings (MPS), 1976-2019 Rate of mass public shootings (MPS), 1976-2019 

3.5 12 

3.0 

10 

2.5 

8 

2.0 

6 

1.5 

4 1.0 

2 0.5 

0.0 0 

Year Year Incidents per 100M 

1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 
 

 

 

Trends in MPS severity 

• Recent rise in severity (6 ave. victim fatalities pre-2015, 12 since)

• Notably Las Vegas, Orlando, Sutherland Springs, and El Paso

0 

20 

40 

60 

80 

100 

120 

1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 

Victims 

Year 

MPS victims fatally shot, 1976-2019 

0 

3 

6 

9 

12 

15 

18 

1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 

Average 

Year 

Average number of MPS victims fatally shot, 1976-2019 
A mass shooting epidemic? 

“We Are In The Midst Of An Epidemic 

Of Mass Shootings” 

Joe Scarborough, Morning Joe 

MSNBC, 2/15/2018 
 

 

An epidemic of fear 

ABC News/Wash Post Poll (Sept 2019): 

Six in 10 fear a mass shootings in 

their community 

Ipsos/USA Today Aug 2019 Poll: 

21% skipped public events where 

there would be a lot of people. 

Source: Chapman University Survey of American Fears 

16.4% 

29.9% 28.1% 

41.5% 41.5% 

0% 

10% 

20% 

30% 

40% 

50% 

2015 2016 2017 2018 2019 

Year 

Afraid or very afraid of mass shootings 
Why the exaggerated sense of risk? 

• Misinterpreted data sets

• Confusion from conflicting definitions

• Amount and nature of media coverage
 

 

Mass confusion and mass shootings 

GVA 2013-2019 

Incidents 2,345 

With 4+ killed 187 

%4+ killed 8% 

Injuries 12,426 

Fatalities* 2,651 

Ave. fatalities 1.1 

*Includes some assailants

No benchmark to assess long-term trend 

0 

100 

200 

300 

400 

500 

2013 2014 2015 2016 2017 2018 2019 

Incidents 

Year 

GVA Mass Shootings (4+ Shot)
Seeing is believing 
 

 

 

What gets covered the most? 

Factor impacting news coverage 

• MPS receive far greater coverage than

family and felony cases (Duwe, 2000)

• Which MPS are particularly newsworthy?

• N=97 MPS incidents, 2000-2019

• Amount of AP State & Local wire coverage

• Major factors: higher death toll, younger

offenders, schools and churches,

terrorism, white victims, arrested assailant

• Fox, Gerdes, Duwe, & Rocque, “The

newsworthiness of mass public shootings:

What factors impact the extent of

coverage.” Homicide Studies, forthcoming.

#Victims killed 

#Victims injured 

Region East 

Midwest 

South 

West* 

Location Government 

School 

Worship 

Off. Age Under 24 

25-39

Off. Race If White 

Contributor Terrorism 

Hate 

Grievance 

Mental illness 

Outcome If Arrested 

%Victims strangers 

%Victims female 

%Victims < 18 yo 

%Victims white 

Interracial event 

N = 97 

+ 0.005

+ 

+ 

+ 0.074

-

+ 

+ 0.059 

+ 0.053

+ 0.044

+ 0.036

+ 0.067

+ 

+ 0.020 

+ 

+ 

+ 

+ 0.030 

+ 

+ 

+ 

+ 0.008 

+
 

 

 

 

 

 

 

Contagion of mass shootings 

• Is there a price to news coverage?

• “Mass Shootings Can Be Contagious, Research

Shows,” NPR, Aug.2019

• “...mass killings involving firearms are incented

by similar events in the immediate past. On

average, this temporary increase in probability

lasts 13 days, and each incident incites at least

0.30 new incidents...” Towers et al. (2015)

• Analyzed the timing of USA Today mass shooting

data (2006-13), but no measurement of media

• Most mass shootings receive little coverage

“Don’t name them; don’t show them” 
 

 

 

A study of contagion 

• Analysis of contagion should reflect the extent of media coverage

• N=6,940 daily counts of mass shooting stories (2000-2018) in the AP wire, major U.S.

newspapers, and network TV news programs and timing of 89 MPS

• Fox, Sanders, Fridel, Duwe, & Rocque, “The contagion of mass shootings: The

interdependence of large-scale massacres and mass media coverage.” (under review)

250 70 

Coverage Victims killed 60 

0 

10 

20 

30 

40 

50 

0 

50 

100 

150 

200 

Victims 

MP Coverage 

Date 
 

 

Media coverage pre/post MPS 

20.0 

17.5 

15.0 

12.5 

13 major daily 

newspapers 10.0 

weighted by 

circulation 

7.5 

5.0 

2.5 

0.0 

Lag/Lead Days 

MP Mean 

2 day lag in peak 

-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
Associated Press 

National Wire 

Network TV 

News 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

AP Mean 

Lag/Lead Days 

1 day lag in peak 

0.0 

0.5 

1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

4.5 

5.0 

-30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

TV Mean 

Lag/Lead Days 

No lag in peak 
 

 

 

Responsible coverage 

• The act v. the actor

• Report facts, not fluff

• Don’t give perpetrator a platform by

publishing rants

• Focus more on strength and

resilience, less on pain and suffering
 

 

 

Rise and fall of social contagion (and public obsession) 

• Eight multiple victim school shooting in 1996-2001

• “School shootings are an epidemic.” Dan Rather, March 5, 2001

• Not another for 4 years

Date Shooter, Age School Location Killed Injured 

2/2/1996 

2/19/1997 

10/1/1997 

12/1/1997 

3/24/1998 

5/21/1998 

4/20/1999 

3/5/2001 

3/21/2005 

Barry Loukaitis, 14 Frontier Junior H.S. 

Evan Ramsey, 16 Bethel Regional H.S. 

Luke Woodham, 16 Pearl H.S. 

Michael Carneal, 14 Heath H.S. 

Mitchell Johnson, 13 & Andrew Golden, 11 Westside M.S. 

Kipland Kinkel, 15 Thurston H.S. 

Eric Harris, 18 & Dylan Klebold, 17 Columbine H.S. 

Charles "Andy" Williams, 15 Santana H.S. 

Jeffrey Weise, 16 Red Lake H.S. 

Moses Lake, WA 

Bethel, AL 

Pearl, MS 

West Paducah, KY 

Jonesboro, AR 

Springfield, OR 

Littleton, CO 

Santee, CA 

Red Lake, MN 

3 1 

2 2 

3 7 

3 5 

5 10 

4 25 

13 23 

2 23 

9 5 

Note: Incidents with 4+ victims and at least two deaths (not including the assailant) 
Looking ahead 

• The Sept. 11, 2001 attack on America diverted attention away from

the threat of multiple victim school shootings

• Might the COVID-19 pandemic pause in mass public shootings

dissipate the social contagion and panic over these incidents?

The 2020 drop in MPS 

12 

9 

6 

3 

0 

Year 

Source: AP/USA Today/Northeastern Univ. Project Incidents 

2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2000 

 

 

 

 

 
 

 

0 

2 

4 

6 

8 

10 

12 

1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 

Incidents 

Year 

Mass public shootings (MPS), 1976-2019 

0 

20 

40 

60 

80 

100 

120 

1976 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 

Victims 

Year 

MPS victims fatally shot, 1976-2019 

Speaking of trends and what 

might lie ahead, what does 

the future hold in terms of 

the severity of MPS? 
Forecasting the Severity of Mass 

Public Shootings in the United States 

‖ Grant Duwe, Ph.D. 

‖ November 2020 

‖ NIJ Webinar 
 

 

 

 

 

 

 

Study Overview 

• The incidence and severity of mass public shootings have increased since the

mid-2000s

• 2017 Las Vegas: 60 people killed and another 411 victims wounded by gunfire

• 2016 Orlando: 49 people killed and another 53 victims injured by gunfire

• What is the likelihood of attacks as catastrophic as Orlando or Las Vegas

occurring in the next 10 years? Or 20 years?

• What is the probability of an even worse mass public shooting taking place in the

future?

• Presentation provides results from our study (under review)

• “Forecasting the Severity of Mass Public Shootings in the United States” by Grant

Duwe, Nathan Sanders, Michael Rocque and James Alan Fox
 

 

 

 

 

Forecasting the Likelihood of Catastrophic Events 

• Research in other fields has shown it’s possible to develop valid estimates of

future likelihood of rare catastrophic events

• Seismology  Earthquake > 7.0 on Richter scale

• Terrorism  Attack similar in magnitude to 9/11

• Heavy-tailed distributions

• Most events are relatively small (low severity) while a small number are very severe

• Mass Public Shootings

• Tend to follow a heavy-tailed distribution

• Relatively few have had more than 10 fatal victims or more than 25 total victims who were shot
 

 

 

 

 

Why It Matters 

• Estimates can help inform decisions about resources

• If the likelihood is very low, then it may be more prudent to divert resources

elsewhere

• But what if the likelihood is greater than 10% (or higher) over the next 5 or 10

years?

• Such an estimate might be relevant for:

• Modeling trauma capacity of regional hospital systems

• Understanding potential consequences of policies relating to firearms or mental health

• Law enforcement assessing risk around large public gatherings
 

 

 

Defining Mass Public Shootings 

• Mass murder = incidents in which 4 or more victims are killed within

24-hour period

• “Mass shooting” = any gun-related mass murder

• “Mass public shooting” = incidents in which 4 or more victims are killed

with a gun in a public location

• Exclude cases in connection w/ other criminal activity

• MPS = most newsworthy mass murders/mass shootings

• Infamous Examples of MPS

• Columbine school shooting: 1999

• Virginia Tech school shooting: 2007

• Las Vegas massacre: 2017

• Make up about 12% of all mass murders
 

 

 

 

 

 

 

 

 

Measuring Mass Public Shootings 

•Triangulated data collection strategy

• FBI’s Supplementary Homicide Reports (SHR)

• Identify when and where mass murders have occurred since 1976

• No information on number of wounded victims or type of location

• News reports

• More detailed info but relying only on news coverage  underreporting

• See Mother Jones or Gun Violence Archive

• Use both  Strategy also adopted by Congressional Research Service and USA

Today

• Consulted both published and unpublished lists

• Consensus review by FDR (Fox, Duwe and Rocque)

• Sample = 156 mass public shootings from 1976-2018

• 2,360 total victims shot, of whom 1,092 were killed
Mass Public Shooting Rate, 1976-2018 

3.50 

3.00 

2.50 

2.00 

1.50 

1.00 

0.50 

0.00 

Mass Public Shooting Rate Per 100 Million 

1976 1981 1986 1991 1996 2001 2006 2011 2016 

YEAR 

MPS Rate 5 per. Mov. Avg. (MPS Rate) 
Severity of Mass Public Shootings, 1976 -2018 

35.00 

MPS Fatality Rate Per 100 Million 

30.00 

25.00 

20.00 

15.00 

10.00 

5.00 

0.00 

1976 1981 1986 1991 1996 2001 2006 2011 2016 

YEAR 

MPS Fatality Rate 5 per. Mov. Avg. (MPS Fatality Rate) 
Severity of Mass Public Shootings, 1976 -2018 

50.00 

45.00 

40.00 

35.00 

30.00 

25.00 

20.00 

15.00 

10.00 

5.00 

0.00 

MPS Total Shot Rate Per 100 Million 

1976 1981 1986 1991 1996 2001 2006 2011 2016 

YEAR 

MPS Total Rate 5 per. Mov. Avg. (MPS Total Rate) 
 

 

 

 

 

 

 

Forecast Assumptions 

• Forecasts influenced by assumptions about future prevalence of mass public

shootings

• Following Clauset and Woodard (2013), 3 sets of assumptions about future

incidence of MPS

• Grounded in historical data from 1976-2018

• Pessimistic: highest prevalence of MPS

• Status Quo: average prevalence of MPS

• Optimistic: lowest prevalence of MPS

• Relied on U.S. Census Bureau projections of U.S. population from 2019-2039

• Calculated anticipated future number of MPS for each year based on size of

U.S. population and MPS rates for each scenario
 

 

 

 

Forecast Parameters 

• Generated 108 independent forecasts • 3 scenarios (pessimistic, status quo and optimistic)

• 3 distributions (Pareto, Weibull and lognormal)

• 3 forecast horizons

• 5 years

• 10 years

• 20 years

• 2 minimum severity cutoffs: 4 victims and 10 victims

• 2 severity outcomes

• Number of victims killed

• 49 (Orlando)

• 60 (Las Vegas)

• 75

• 100

• Number of victims shot (killed and wounded)

• 100

• 250

• 500

• 1,000
 

 

 

 

 

 

 

 

 

 

 

Results for Number of Victims Killed by Gunfire 

• Estimates varied across forecast parameters but...

• ...even under optimistic conditions over next 10 years:

• At least 38% for attack as lethal as Orlando

• At least 26% for attack as lethal as Las Vegas

• At least 16% for MPS with at least 75 fatal victims

• At least 9% for MPS with at least 100 fatal victims

• ...and under pessimistic conditions over next 10 years:

• At least 51% for attack as lethal as Orlando

• At least 37% for attack as lethal as Las Vegas

• At least 24% for MPS with at least 75 fatal victims

• At least 13% for MPS with at least 100 fatal victims
Fatal Victim Results for Lognormal Model 
 

 

 

 

 

 

 

 

 

Results for Total Number of Victims Shot 

• Under optimistic conditions over next 10 years:

• At least 41% for MPS with at least 100 victims shot

• At least 5% for MPS with at least 250 victims shot

• At least 0.6% for MPS with at least 500 victims shot

• At least 0.05% for MPS with at least 1,000 victims shot

• Under pessimistic conditions over next 10 years:

• At least 56% for MPS with at least 100 victims shot

• At least 8% for MPS with at least 250 victims shot

• At least 1% for MPS with at least 500 victims shot

• At least 0.08% for MPS with at least 1,000 victims shot
 

 

 

 

 

 

Summary of Results 

• Regardless of forecast parameters used, odds are very low we’ll see MPS with as

many total gunfire victims as Las Vegas (500+) in near future.

• Odds are higher when focusing on fatalities

• Even under optimistic conditions, at least:

• 26% for a MPS with 60 victims killed

• 9% for a MPS with 100 victims killed

• Likelihood of a MPS as bad as Las Vegas or worse is not trivial

• Resource allocation decisions

• Law enforcement

• Medial professionals

• Policymakers
 

 

 

 

Final Thoughts 

• Main Limitations

• Study cannot tell us where or exactly when a severe MPS may transpire

• Variability across parameters

• Estimates strongly depend on assumptions made about type of

distribution and tail location

• Drew upon strategy used in other disciplines that’s novel for criminology

• Provides sound methodology to predict probability of mass casualty

events

• May be applied to other types of violence (often heavy-tailed

distribution)

• Example: serial murder
 

 

 

The Effect of State Gun Laws on Mass 

Public Shootings; and 

Exploring Averted Incidents 

Michael Rocque, PhD 

Bates College 

Findings from NIJ funded studies to advance understanding and inform prevention of public November 18, 2020 

mass shootings, Part 1. 

1 
Gun laws vary by state Public/Policy interest 

• Fear

• Media attention

https://www.theguardian.com/world/interactive/2013/jan/15/gun-laws-united-states 

State gun laws & MPS 

November 18, 2020 

2 
• Theory-gun availability (Cook, 1983)

• Mechanisms

• Direct, routine activities

• Indirect, motivation

Motivated 

offender 

Gun MPS 

availability 

Gun 

availability 

Motivation MPS 

Background 

November 18, 2020 

3 
 

 

 

 

• Three studies find support for stricter gun laws

• Gius (2015)

• AWB lower severity

• Klarevas et al. (2019)

• LCM bans lower severity

• Webster et al. (2020)

• LCM bans lower incidence

• Limitations

• Unclear definitions of state laws

• Mass shooting data

Previous work 

November 18, 2020 

4 
 

 

 

 

• Data from 1976 to 2018 on 89 state gun laws and MPS by state

State Laws: 

1) AWB 

2) LCM bans

3) Permits

4) Extreme-risk protection orders

5) Universal background checks

6) May-issue concealed-carry laws

7) Relinquishment of guns for those prohibited

8) Violent misdemeanor prohibitions

• MPS dataset: triangulated approach

• SHR, existing databases, news stories

Current study 

Siegel, M., Goder-Reiser, M., Duwe, G., Rocque, M., Fox, J. A., & Fridel, E. E. (2020). The relation between state gun laws and the incidence and severity of 

mass public shootings in the United States, 1976–2018. Law and Human Behavior, 44(5), 347. 

November 18, 2020 

5 
 

 

 

Models: 

1) Logistic regression for incidence

2) Zero-inflated negative binomial for incidence and number of fatalities/victims

Red=in count models 

Current study 

Controls: 

a) State pop

b) Pop density

c) Black (proportion)

d) Male 15-29 (proportion)

e) Poverty rate

f) Unemployment rate

g) Alcohol consumption

h) Divorce rate

i) Firearm homicide rate

j) Suicide rate

k) Incarceration rate

l) Household gun ownership

m) Violent crime rate

November 18, 2020 

6 
Total numbers 

Varying incidence 

Created with Adobe Spark 

Results 

November 18, 2020 

7 
Statistically sig p <.05, LCM is for severity model 

Results: Gun Laws 

November 18, 2020 

8 
 

AVERTED MASS PUBLIC SHOOTINGS 

(with Madison Gerdes and Maddy Clark) 

• Research on MPS

• Individual, contextual, historical factors

• Leakage, threats (Duwe, 2017; Lankford et al., 2019; Silver et al., 2018 (FBI))

• But what about planned events that were stopped?

• Do they look like completed cases?

• Can we learn points of intervention to help prevent future events?

Studying averted MPS 

November 18, 2020 

9 
 

 

 

• Pre-attack behaviors:

• 77% >week

• 4-5 concerning behaviors

• Averted MPS

• Warning signs common

• Younger, white, more partners,

less target specific Existing research 

November 18, 2020 

10 
• Different completed data

• Different credibility assessment

• Different data sources

Our project 

November 18, 2020 

11 
 

 

 

• “Any plot, plan, or threat to shoot four or more individuals in a

public location within a 24-hour period, absent of other criminal

activity (e.g., robberies, drug deals, gang conflict, etc.), in which no

injuries (other than to the perpetrator) occurred.”

• Must be credible (specific plan or threat with access to weapon)

• Plan must be detailed (e.g., maps, targets) or weapons must be

accessible. Silva required gun or plan to acquire gun.

Definition 

November 18, 2020 

12 
 

A multi-pronged approach 

Existing databases: Potential cases identified: 

• Madfis, n=237 • Each case reviewed (2 researchers)

• Agnich, n=32 • Disagreements resolved

• Sarteschi, n=38 credible, 22

non

• Averted School Violence

• K-12 School Shooting

Database

• Online lists (e.g., ABC)

• Lexis Uni searches

Methods 

November 18, 2020 

13 
• Codebook • Variable information

developed and gathered via open sources

data collection (news stories, online

starting in corrections databases)

summer 2019

• Three coders, with discussion

to resolve questions

Methods 

November 18, 2020 

14 
 

• Reliability Assessment (Summer, 2020)

• First a trial, then 10 case reliability assessment

• Coding focused on “subjective” fields (mental illness, plan/threat

length, response, motivation, and credibility)

• Percent agreement: 47-93%

• Gwet’s AC: MI=.73; Threat=.40; Plan=.86, Credibility=.92 

• Response and Motivation=text but good agreement, 100% for

response and 93% for motivation

Methods 

November 18, 2020 

15 
 

• Lots of missing data, information hidden

• When to move on

• Coding

• Length variables problematic, initially in days, recoded to categories

• Focused on credibility for agreement

• At least two coders reviewed every case

• WhatsApp to the rescue!

Challenges 

November 18, 2020 

16 
• As of November, 2020: 210 cases

• Date range: 1999-2019

• Offender/incident structured

• Mostly quantitative, some text (motivation/response, location)

• Database is in progress

Database 

November 18, 2020 

17 
MI=mental illness; any discussion or diagnosis of mental illness for any suspect involved in a case 

Comparison 

November 18, 2020 

18 
 

 

• Permit/LCM bans related to incidence and severity of MPS across

states

• Mechanism unclear

• Averted MPS project continuing

• Some similarities and differences

• Future work will explore the plans in detail to help guide

intervention efforts

Conclusion 

November 18, 2020 

19 
Thank you 

Questions and Answers 

Please submit questions to “all panelists” in the Q&A box. 

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