It's the capital of the free world and the murder capital of the United States.

In just one night last week, three people were killed in the District of Columbia. Typically, all were shootings and all, police said, could be drug-related.By Wednesday, 75 people had been killed this year in Washington, compared with 46 by the same time in 1988. Last year set a city record with 372 homicides - virtually one a day and 145 more than in 1987.

At the current rate, the city could log more than 600 murders this year.

The pace of the killings in 1988 - 59.4 for each 100,000 residents - gave Washington a distinction it didn't want: Murder Capital USA. Detroit, which held the title in 1987, had 58 murders per 100,000 residents.

Why Washington?

Police officers and experts agree: handguns and a sudden influx of cheap drugs.

Both are easy to come by and both are increasingly finding their way into the hands of young Washingtonians, many of whom have become armed delivery people caught in wars between drug gangs.

Ten of the 42 people killed in October were teen-agers. Seven more were in their early 20s.

It wasn't always so.

"Washington didn't become a target for the drug trade as early as other large cities did," said Gwynne Peirson, a retired criminology professor at Howard University who spent 23 years as a police officer in Oakland, Calif. "It's a relatively recent phenomenon here because the population of Washington isn't the size of many other cities, so it wasn't as attractive a market initially."

That changed with the coming of crack, a highly potent and addictive - but cheap to get hooked on - form of cocaine that can be smoked.

A typical dose of 100 milligrams, which a regular user might smoke a dozen or more times a day, sells on the street for about $10, said Maurice Hill of the Drug Enforcement Administration. A 75-milligram "starter" dose often goes for $5.

"The average kid with an allowance can buy crack unimpeded," said Mario Perez, a DEA agent. "All he has to do is shake hands with his best buddy outside the school house."

One expert said the very nature of crack has driven up the murder rate.

"There's something about the nature of crack that makes people crazy, makes them impulsive and likely to do irrational things," said Hubert Williams of the Police Foundation, a research organization.

"I've heard crack addicts say use of crack opens up every pleasure center in the body," said Williams, who was a police officer for 24 years in Newark, N.J. "The sensations are so high and also so short in terms of duration that almost after taking the first one, you need a second one because you're on a downer. So you have an ideal set of circumstances to create a huge market."

Then there is the presence of guns.

Ten to 20 years ago, high school students might have carried pen knives as protection. Today, said a city officer who requested anonymity, the protection is a handgun, often an automatic.

"We have people who are settling their arguments with guns," he said.

Of the almost 1,600 weapons seized by police since late 1986 through Operation Clean Sweep, an undercover operation aimed at drug dealers, more than 1,200 have been handguns.

To all that, add the high unemployment rate among the city's black teens. In 1987, the last full year for which statistics are available, 22.4 percent had looked for legitimate work, but failed.

"It's an easy market with so many poor, unskilled black people willing to take the small risk," Peirson said. "With people that are uneducated and unskilled, the idea of standing out on a street making $500 to $1,000 a night with the chances of getting caught relatively small, it's a small risk."