The eight fatalities from Tuesday’s Manhattan terror attack will be included in the city’s homicide total for 2017 when, as expected, the NYPD and Mayor Bill de Blasio announce the latest data Friday on serious crime in the five boroughs, a police spokesman said.

Adding the eight victims, who were mowed down when a suspected ISIS-inspired terrorist drove a rental truck on a West Side bike path, to the city’s homicide count for 2017 won’t slow a record downward trend that could see the fewest number of killings in the modern era of police record keeping by year’s end.

“It all depends,” said one NYPD official, alluding to the unpredictability of crime and terrorism.

With about eight weeks to go in the year, the NYPD has recorded 237 homicides, compared with 290 at the same time in 2016, a decline of 18.2 percent, the spokesman said. 

The only time in recent history that mass casualty statistics weren’t included in the regular homicide count was after the Sept. 11, 2001 terror attacks when the 2,753 deaths were kept separate from the city’s official homicide total of 649.

After the March 1990 Happy Land Social Club arson fire in the Bronx took 87 lives, police included those deaths in the regular count of homicides that year — a record high of 2,245. In the early 20th Century, killings in the notorious Chinatown Tong Wars garnered a separate asterisk in record books.

Last year there were 335 homicides in the city. The lowest number of homicides recorded in the modern data-keeping era was 333 in 2014.

The downward trend also applies to other types of serious crimes, according to police data through Nov. 1.

Shootings are down to 677, or 22 percent from 870 in the same period in 2016, according to the latest data. Police officials think that the city is on track to break last year’s record low in shootings of 998.

Richard Aborn president of the Citizens Crime Commission of New York City, said the continuing decline in homicides and shootings stems not only from smarter policing but a more stable crime picture overall.

“I think what is happening is that the NYPD is getting better and better at precision policing,” Aborn said. “. . . instead of flooding high crime areas with many cops, they are focusing on repeat offenders.”

Aborn said much of the crime in the city is likely committed by a small number of offenders, something NYPD officials have stressed in recent months.