evidence: President Donald Trump has said major US cities are seeing a spike in crime, and has offered to send in federal law enforcement to tackle the situation. [...] President Trump has also pointed to a string of shootings in recent months, and shooting incidents in Chicago are up by more than 60% compared to the same point last year. [...] Other cities earmarked by President Trump have also seen mixed trends. Murders are down in Baltimore, but up in Oakland and Detroit compared with the same time last year.