Explanatory Note - Stop Data
4/18/2023
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Background: In July 2019, the Metropolitan Police Department (MPD) implemented new data collection
methods that enabled officers to collect more comprehensive information about each police stop in an
aggregated manner. More specifically, these changes have allowed for more detailed data collection on
stops, protective pat down (PPDs), searches, and arrests. (For a complete list of terms, see the glossary
on page 2.) These changes support data collection requirements in the Neighborhood Engagement
Achieves Results Amendment Act of 2016 (NEAR Act).
Data Notes: The accompanying data cover all MPD stops including vehicle, pedestrian, bicycle, and
harbor stops for the period from July 1 – December 31, 2021. A stop may involve a ticket (actual or
warning), investigatory stop, protective pat down, search, or arrest.
If the final outcome of a stop results in an actual or warning ticket, the ticket serves as the official
documentation for the stop. The information provided in the ticket include the subject’s name, race,
gender, reason for the stop, and duration. All stops resulting in additional law enforcement actions (e.g.,
pat down, search, or arrest) are documented in MPD’s Record Management System (RMS). This dataset
includes records pulled from both the ticket (District of Columbia Department of Motor Vehicles [DMV])
and RMS sources. Data variables not applicable to a particular stop are indicated as “NULL.” For
example, if the stop type (“stop_type” field) is a “ticket stop,” then the fields: “stop_reason_nonticket”
and “stop_reason_harbor” will be “NULL.”
Each row in the data represents an individual stop of a single person, and that row reveals any and all
recorded outcomes of that stop (including information about any actual or warning tickets issued,
searches conducted, arrests made, etc.). A single traffic stop may generate multiple tickets, including
actual, warning, and/or voided tickets. Additionally, an individual who is stopped and receives a traffic
ticket may also be stopped for investigatory purposes, patted down, searched, and/or arrested. If any of
these situations occur, the “stop_type” field would be labeled “Ticket and Non-Ticket Stop.” If an
individual is searched, MPD differentiates between person and property searches. Please note that the
term property in this context refers to a person’s belongings and not a physical building. The
“stop_location_block” field represents the block-level location of the stop and/or a street name.
The age of the person being stopped is calculated based on the time between the person’s date of birth
and the date of the stop.
There are certain locations that have a high prevalence of non-ticket stops. These can be attributed to
some centralized processing locations. Additionally, there is a time lag for data on some ticket stops as
roughly 20 percent of tickets are handwritten. In these instances, the handwritten traffic tickets are
delivered by MPD to the DMV, and then entered into data systems by DMV contractors.
On August 1, 2021, MPD transitioned to a new version of its current records management system,
Mark43 RMS.
Due to this transition, the data collection and structures for the period between August 1, 2021 –
December 31, 2021 were changed. The list below provides explanatory notes to consider when using
this dataset.
• New fields for data collection resulted in an increase of outliers in stop duration (affecting 0.98%
of stops). In order to mitigate the disruption of outliers on any analysis, these values have been
set to null as consistent with past practices.
• Due to changes to the data structure that occurred after August 1, 2021, six attributes pertaining
Explanatory Note - Stop Data
4/18/2023
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to reasons for searches of property and person are only available for the first seven months of
2021. These attributes are: Individual’s Actions, Information Obtained from Law Enforcement
Sources, Information Obtained from Witnesses or Informants, Characteristics of an Armed
Individual, Nature of the Alleged Crime, Prior Knowledge. These data structure changes have
been updated to include these attributes going forward (as of April 23, 2022).
• Out of the four attributes for types of property search, warrant property search is only available
for the first seven months of 2021. Data structure changes were made to include this type of
property search in future datasets.
• The following chart shows how certain property search fields were aligned prior to and after
August 1, 2021. As of August 2, 2022, these fields have reverted to the original alignment.
Attribute Type
Before Aug 1st
After August 1st
Property Search Object
Residence/Other Building
Other
Property Search Reason
Warrant (warrant search
only)
Warrant
Property Search Reason
Consent (consent search
only)
Consensual
Property Search Item
Seized
Narcotics
Contraband
Property Search Item
Seized
Stolen Property
Contraband
Property Search Item
Seized
Gun
Weapon
Property Search Item
Seized
Other Weapon
Weapon
Property Search Item
Seized
Drug Paraphernalia
Contraband
Property Search Item
Seized
Narcotics
Drugs/narcotics
Property Search Item
Seized
Stolen Property
Suspected stolen property
Property Search Item
Seized
Gun
Firearms
Property Search Item
Seized
Other
Other contraband or
evidence
Property Search Item
Seized
Other Weapon
Weapon(s) other than
firearm
In October 2022 several fields were added to the dataset to provide additional clarity differentiating
NOIs issued to bicycles (including Personal Mobility Devices, aka stand-on scooters), pedestrians, and
vehicles as well as stops related specifically to MPD’s Harbor Patrol Unit and stops of an investigative
nature where a police report was written. Please refer to the Data Dictionary for field definitions.
In March 2023 an indicator was added to the data which reflects stops related to traffic enforcement
and/or traffic violations. This indicator will be 1 if a stop originated as a traffic stop (including both stops
where only a ticket was issued as well as stops that ultimately resulted in police action such as a search
or arrest), involved an arrest for a traffic violation, and/or if the reason for the stop was Response to
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Crash, Observed Moving Violation, Observed Equipment Violation, or Traffic Violation.
Between November 2021 and February 2022 several fields pertaining to items seized during searches of
a person were not available for officers to use, leading to the data showing that no objects were seized
pursuant to person searches during this time period.
Finally, MPD is conducting on-going data audits on all data for thorough and complete information. Figures
are subject to change due to delayed reporting, on-going data quality audits, and data improvement
processes.
Explanatory Note - Stop Data
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Glossary
• Consent search: A search of a person or property based upon valid consent of the individual
whose person or property is being searched. The Fourth Amendment requires that consent to a
search not be coerced, by explicit or implicit means, by implied threat, or covert force.
• Contact or field contact: Conduct by a police officer which places the officer in face-to-face
communication with an individual under circumstances in which the individual is free not to
respond and to leave.
• Probable cause: A set of facts, circumstances, or reliable information that would lead a
reasonable and prudent police officer to believe that a crime has been committed, or is about
to be committed, and that a certain person committed it.
• Probable cause search: A warrantless search of a person or vehicle based upon probable cause
that is conducted under specific circumstances. To conduct a probable cause search of a
vehicle, a police officer must have probable cause to believe that contraband or physical
evidence of a crime is in a moveable (i.e., operable) vehicle in a public area (e.g., public space,
shopping center, parking lot). To conduct a probable cause search of a person, a police officer
must have probable cause to believe that the person has contraband or physical evidence of a
crime on his or her person.
• Protective pat down: A limited protective search for concealed weapons or dangerous
instruments. A pat down, also known as a frisk, consists of patting an individual’s outer clothing
to determine the presence of weapons and other dangerous objects. Pursuant to the Supreme
Court ruling in Terry v. Ohio, 392 U.S. 1 (1968), police officers have authority to conduct a limited
search of a person for weapons during some stops. Reasonable suspicion for a stop does not
automatically provide the basis for a pat down. For a pat down to be reasonable and
constitutional under the Fourth Amendment, the preceding stop of the individual’s person
must be lawful and the police must have an objectively reasonable basis to believe that the
individual is armed and dangerous.
• Reasonable suspicion: Minimal level of objective justification for making a stop. Although
reasonable suspicion is not capable of precise definition, it is more than a hunch or mere
speculation, but less than probable cause.
• Records Management System: Computer system used by MPD to collect and store required
stop data as well as other law enforcement information including crimes, arrests, missing
person reports, and traffic crashes.
• Stop: A temporary investigative detention of a person for the purpose of determining whether
probable cause exists to make an arrest. A stop is a seizure of an individual’s person and occurs
whenever an officer uses his or her authority to compel a person to halt, remain in a certain
place, or to perform an act (such as walking to a nearby location where the police officer can
use a radio or telephone). If a person is under a reasonable impression that he or she is not free
to leave the police officer’s presence, a stop has occurred.
• Warrant search: A search conducted pursuant to a valid search warrant granted by a judge or
magistrate based upon probable cause.
