Data and Methods
The bulk of this database was collected through public records requests to the many authorities involved in the complex medicolegal system on the US-Mexico border. Most of these sources are described below, but we also requested data from various other agencies in order to fill in supplemental data, for example the New Mexico Department of Transportation, which allowed us to get more information about cases involving vehicle accidents or Border Patrol pursuits.
When possible, we requested this data informally. We responded to requests that were ignored or outright denied with formal public records requests, and, in the case of Imperial County, escalated to a lawsuit.
To ensure precise request language, we adopted 2014 guidelines outlined by the University of Arizona Binational Migration Institute, as well as definitions formulated by the newer Migrant Mortality Mapping Project. Our requests sought data on “person(s) who died in the process of furthering their entrance into the United States from Mexico between ports of entry, regardless of their intention to migrate.” In addition to requesting the decedent’s demographic information (age, sex, ethnicity, nationality), we also requested information around the manner of death (date of recovery, cause of death, description of physical remains, case number, location of death), and incident narratives that contextualized the death and included information about potential CBP involvement.
We removed cases that were not related to border crossings, as well as adding new cases and requesting additional data where it seemed that there were gaps. We compared coordinates with their written descriptions, added coordinates when a physical address or description was listed, and used incident narratives to approximate Type of Incident and CBP-Related death designations used in the “BSITS” and “OPR” databases discussed below.
In total, our dataset aggregates data from the San Diego County Medical Examiner, Imperial County Coroner, Yuma County Medical Examiner, Pima County Office of the Medical Examiner, New Mexico Office of the Medical Investigator, El Paso County Office of the Medical Examiner, Webb County Medical Examiner, various Sheriff’s offices and Justices of the Peace throughout Texas, Customs and Border Protection, the Office of Professional Responsibility, and the National Immigration Institute(Mexico), as well as various other agencies used to fill in certain details. The level of detail in each individual region varies greatly by data source, as detailed below:
- San Diego County Office of the Medical Examiner
Migrant mortality data in San Diego County was obtained through multiple, informal records requests to the San Diego County Medical Examiner (SDCME). The SDCME was generally very responsive and avoided the unintentionally demeaning language typically used by other medical examiners’ offices to describe migrants.
We were provided a spreadsheet of all deaths related to border-crossings. This includes detailed narrative data that preempted us requesting reports for each death. However, it is unclear exactly how the records custodian searched or defined migrant deaths in their database, potentially resulting in the exclusion of some deaths.
One such case includes a Guinean woman who died while waiting in a makeshift camp outside of the San Ysidro Port of Entry. When we reached out to the medical examiner for an explanation, the records custodian erroneously cited the fact that the woman was waiting to be processed at a port of entry. In reality, she died in what amounted to an open air detention center precisely because the port of entry had been closed to asylum seekers. Other similar cases may have been excluded as well.
2. Imperial County Coroner
Imperial County rests on the southeastern corner of California and straddles two Border Patrol Sectors: El Centro and Yuma. Deaths are processed by the Imperial County Coroner, which is a part of the Imperial County Sheriff’s Office. In order to make more accurate comparisons with BP data we combined Imperial and Yuma Counties to compare with BP’s combined El Centro and Yuma Sectors.
Our records requests were denied or ignored. After many months of appeals and denials we moved forward with litigation to gain access to the records with the help of attorney Abenicio Cisneros.
In response to legal action we eventually received a spreadsheet with minimal data and no explanation for how the records custodian had compiled the data. We requested investigator’s reports for each case, which the Coroner’s office has slowly been providing (though there are concerning issues, such as missing documents and 32 cases for which proper autopsies had not been completed). As these new materials arrive, data from this county will be expanded to include flags for CBP-related cases, deaths of US residents, and other fields and comparisons to CBP’s own data.
3. Yuma County Medical Examiner
Yuma County stretches along the remote western Arizona desert, from the California border to Pima County, just west of the town of Ajo. It is fully contained within CBP’s Yuma Sector, though that Sector continues on into Imperial County in California. In order to make more accurate comparisons with BP data we combined Imperial and Yuma Counties to compare with BP’s combined El Centro and Yuma Sectors.
The Medical Examiner for Yuma County is also part of the Sheriff’s department. A spreadsheet of migrant death data was provided in response to a records request, and a follow-up request resulted in the provision of individual investigators reports for each case. We used these reports to populate the spreadsheet with comparisons to BP data, as well as identify US residents, asylum seekers, CBP-related deaths, and other fields.
4. Pima County Office of the Medical Examiner
Pima County Office of the Medical Examiner, who aggregates data from all southern Arizona counties (excluding Yuma County) to create its database. This region mirrors the geographical area of CBP’s Tucson sector, and for years has been the primary indispensable data source for studies of migrant deaths.
We’ve included the spreadsheet provided by Humane Borders, unedited, in this database and map. Humane Borders receives monthly mortality data directly from the PCOME.
We have recently received records responsive to a request for reports that would allow us to track CBP-related deaths and other circumstances, and relevant updates to the spreadsheet are ongoing. For recent research into CBP-related deaths in the Tucson sector, see this report by Robin Reineke and Daniel Martinez in the 2024 issue of the Journal on Migration and Human Security.
5. New Mexico, El Paso County, and Hudspeth County
Data from the regions comprising the El Paso sector were compiled as part of No More Deaths’ previous abuse documentation project, The El Paso Migrant Death Database. Detailed information on methodology, as well as other findings, can be found on that website.
5. South Texas
South Texas data was graciously shared by Stephanie Leutert from the University of Texas at Austin. The state of Texas has an incredibly complex system of death investigation which is difficult to access and navigate, with medical examiners, Justices of the Peace, or Sheriff’s departments variously taking on forensic duties and identification of migrant deaths, and often authorities from other counties take on these duties on behalf of other districts. Leutert’s data comes from countless public records requests and in-person visits and interviews. While this data will be released in other venues, an approximate methodology is available for an earlier iteration of this database published by the Strauss Center.
We filled in gaps in this dataset using CBP data, but there are many duplicates, and still many missing cases. Texas data should therefore not be used to create an accurate overall count of migrant deaths, and also should not be used as a comparison to CBP’s own reporting.
6. Customs and Border Protection (CBP)
Customs and Border Protection tracks migrant deaths in two databases. BSITS (Border Safety Initiative Tracking System), records deaths of all migrant deaths within a “target zone” of the US-Mexico border (though this also includes the Miami Sector and now areas of the US-Canada border, which has recently seen unprecedented border crossing deaths). NMD obtained BSITS data through a FOIA request from CBP, which included demographic and person-level data detailed enough to compare each case to other databases. Additional data was supplemented by a FOIA from Stephanie Leutert, which contained incorrectly-redacted GPS coordinates and other more detailed fields from 1997 through 2017. The BSITS database spans all sectors from 1997, when CBP began tracking these deaths, through 10/10/24, when CBP provided records responsive to our request.
CBP-related deaths are tracked by the Office of Professional Responsibility (OPR) in another database. The OPR has been tasked since 2021 with investigating CBP-related deaths, after the entity who previously handled these cases, the Critical Incident Teams (BPCITs), were disbanded in 2022 following investigation into their role in mishandling or covering up CBP involvement in migrant deaths. OPR continues to be criticized for its response to CBP-related deaths. OPR databases were obtained for fiscal year 2022 by Andrew Free, for 2013 through January 2024 by Stephanie Leutert, and for 2013-2025 by Bryce Peterson. Each of these requests yielded slightly different results and numbers of cases. Together they account for 208 deaths investigated by BPCITs or OPR, with as yet no clear reason for the discrepancy between these records. OPR’s own reporting cites “171 deaths which occurred during FY 2022, including 52 in-custody deaths, 68 reportable CBP-involved deaths that were not in-custody, and 51 additional deaths that Appropriations staff requested to be included in this report.”
Many issues with CBP’s data collection have been documented by journalists, researchers (including NMD’s previous report), as well as the Government Accountability Office (GAO), who investigated and denounced CBP’s data collection in 2006, 2022, 2023, and 2025. These inaccuracies led us to create this larger database and compare, case by case, each migrant death recorded by CBP. Countless misspellings, incorrect dates, ages, duplicate cases, and other typographical made these comparisons very difficult.
7. Grupos Beta / Other Mexican Data Sources
Grupos Betas are government-run humanitarian groups administered by the Mexican National Institute of Migration. They are tasked with providing food, water, and information to migrants. They are also involved in search and recovery efforts. Through a public records request issued via the Plataforma Nacional de Transparencia, we obtained a spreadsheet containing deaths recorded by Grupos Betas since 1997. This dataset contained minimal location and demographic data.
We also obtained data through public records requests for other medicolegal authorities in Northern Mexico which showed, among other things, large numbers of deaths of people who died in the Rio Grande but whose bodies ended up on the Mexican side of the river, including individual deaths where BP had chased the person into the river. We are still working through all of this data, which is essential for understanding and showing how the deaths caused by Prevention Through Deterrence go far beyond the narrow strip of land on this side of the US-Mexico border.