WASHINGTON (AFP) - After following a DNA lead gleaned from pizza crust, US authorities have arrested a suspect in the grisly murder of three members of a wealthy Washington family and their maid.

Daron Dylon Wint, 34, was arrested on Thursday night in the nation's capital, Washington Metropolitan Police said.

Three other men and two women who were with Wint as police pounced late Thursday night were also arrested, a US Marshals Service official said.

The case has shocked the city because of the violence employed in last week's murders - one of the four bludgeoned victims was a 10-year-old boy - and because the neighbourhood where it happened is posh and hardly used to such bloodshed.

The manhunt for Wint began after the DNA was collected from pizza delivered to the slain family's home and matched to him. The chase stretched all the way up to New York where he was said to have relatives.

In fact, he was arrested after having returned from that city, authorities said.

In the crime, businessman Savvas Savopoulos, president and CEO of American Iron Works, a building materials company in Maryland, his wife Amy, their 10-year-old son Philip and the family's housekeeper Veralicia Figueroa - were found bound and bludgeoned on May 14 after a fire gutted the millionaire's mansion.

Wint used to work for that company, officials say.

The motive of the killing is not known.

But police say that while the family was being held, an assistant of Savopoulos delivered US$40,000 (S$53,480) in cash to the home.

Savopoulos's blue Porsche turned up shortly after the murders, abandoned several miles from the crime scene, authorities said. It also had been set ablaze.

- First degree murder charge -

Wint is now charged with first degree felony murder while armed.

He was captured with five other people - three men and two women - who were also arrested.

US Marshals tailed two cars as they left a hotel in the neighboring state of Maryland, Commander Robert Fernandez of the US Marshals Service said Friday.

"We could tell that they were together. They were going north bound. They did sort of a strange U-turn and we suspected they may have thought that they were being tailed," Fernandez said.

"Once we reached a location in DC where we felt we could take them down, we did a pin manoeuvre on both vehicles and we arrested everyone," he added.

The Washington Post reported Friday that Wint has had several brushes with the law over the years, often for allegedly violent behavior.

But Wint's former attorney said on CNN on Friday that the police have the wrong man.

"It's not his act. He's a nice guy. He's patriotic," lawyer Robin Fickers said. He said he had defended Wint in six cases in 2005 and 2006 and he was never found guilty.

Fickers said Wint is being tried in the media, criticizing Mayor Muriel Bowser for holding a press conference to name Wint before he had even been questioned.

Fickers also challenged the pizza evidence, saying authorities have not said where the pizza was when it was found.

"Was it in the trash behind the house?" he asked. "I've had many cases where the DNA results were thrown out of court because they simply were not valid. And they may well have been contrived in this case."