County profile
Mercer County
15 law enforcement agencies reported internal affairs activity for 2025.
IA investigations, 2025
361[1]
Sworn officers, 2025
245[1]
Agencies in Mercer County
| Agency | Type | Officers | Investigations | Incidents | Major discipline |
|---|---|---|---|---|---|
| Trenton PDCivil service | Municipal police | 95 | 155 | 130 | 44 |
| Lawrence Twp PDCivil service | Municipal police | 32 | 47 | 39 | 4 |
| Ewing Twp PDCivil service | Municipal police | 26 | 33 | 22 | 1 |
| Princeton University Police | Municipal police | 12 | 24 | 20 | 0 |
| Robbinsville Twp PD | Municipal police | 14 | 19 | 13 | 1 |
| Princeton PD | Municipal police | 14 | 18 | 15 | 0 |
| East Windsor Twp PD | Municipal police | 11 | 17 | 14 | 1 |
| Hamilton Twp PDCivil service | Municipal police | 10 | 12 | 11 | 0 |
| West Windsor Twp PD | Municipal police | 6 | 8 | 3 | 1 |
| College Of New Jersey PD | Municipal police | 6 | 7 | 5 | 0 |
| Hightstown PD | Municipal police | 5 | 6 | 6 | 0 |
| Hopewell Twp PD | Municipal police | 6 | 6 | 5 | 4 |
| Mercer Co Sheriffs DeptCivil service | County sheriff | 4 | 4 | 4 | 0 |
| Pennington Boro PD | Municipal police | 3 | 4 | 2 | 1 |
| Mercer Co Prosecutor Office | County prosecutor | 1 | 1 | 1 | 0 |
| Hamilton Twp PD - Mercer CountyCivil service | Municipal police | not reported | not reported | not reported | 3 |
| Mercer County Prosecutors Office | County prosecutor | not reported | not reported | not reported | 3 |
| Mercer County Sheriffs OfficeCivil service | County sheriff | not reported | not reported | not reported | 4 |
| Princeton University PD | Municipal police | not reported | not reported | not reported | 9 |
IA totals are for 2025; major discipline counts span 2020-2025. 7 of these agencies are in civil service jurisdictions governed by the Title 4A discipline framework (see the full local jurisdiction roster).
Questions and answers
- How many internal affairs investigations did Mercer County report in 2025?
- Agencies in Mercer County reported 361 internal affairs investigations in 2025, across 15 reporting agencies, according to New Jersey Attorney General data.
- How many police major discipline records are there in Mercer County?
- Mercer County agencies have 76 major discipline records in the Attorney General's 2020-2025 releases, including 19 terminations. These are final, adjudicated actions.
Sources
- [1]New Jersey Internal Affairs Agency Totals, 2021-2025. New Jersey Office of the Attorney General. Sheet "Sheet1", row 1. Snapshot retrieved 2026-06-09. County totals summed over Mercer County agency rows for 2025; row 1 is the header. ↩
- [2]New Jersey Major Discipline Data, 2020-2025. New Jersey Office of the Attorney General. Sheet "Major Discipline Data", row 1. Snapshot retrieved 2026-07-03. Record counts from Mercer County rows, all years; row 1 is the header. ↩