Police chiefs in several sanctuary cities have argued that when immigrant communities fear deportation from contact with police, victims and witnesses become less likely to report crimes, undermining public safety broadly. Several police chiefs have specifically testified that trust-building with immigrant communities, built over years, can erode quickly once local police are seen as an extension of federal immigration enforcement. Advocates argue this erosion of trust can take years to rebuild once it's lost, with lasting effects on public safety. They see protecting this trust as a practical, not just ideological, priority.