"It's not hard," said Marzah. "You hit them against the wall, throw them in a pit, or in the river, and they are dead. And then you give the report to Charles Taylor."
Marzah said he had been part of a special unit that Taylor had set up called "No Baby on Target", adding: "He said we should execute any baby we saw. After we did that, he gave us money."
Fighters had also used knives to cut open pregnant women, he added.
How can anybody do something like this to another person, is truly beyond words.
This asshole has to pay for what he did.
During the war in Liberia they would mount ambushes on civilians, said Marzah.
"At the checkpoint we used human intestines and sometimes put heads on sticks to scare people," he said. And the same thing went on in Sierra Leone, he added.
Both Sierra Leone's RUF rebels and the Liberian fighters of the NPFL operated under Taylor's command, he said.
There was no RUF as such, he said. "From Freetown to Liberia there was one organisation, all answering to Taylor."
Taylor was in constant touch with the RUF leaders by satellite telephone and radio links, said Marzah.
Some of those leaders frequently visited the Liberian capital Monrovia to deliver diamonds, receive their orders and pick up weapons.
Prosecutors accused Taylor of having amassed a 600-million-dollar (385-million-euro) fortune.
Marzah told the court Taylor ordered him to take arms to Sierra Leone rebels and exchange them for diamonds.
In the early 1990s he went to Sierra Leone some 40 times with transports carrying AK-47 assault rifles and rockets.
"Sometimes, we got ammunition from White Flower (Taylor's presidential residence) or a Russian plane," said Marzah, 49.
"By Charles Taylor's directive, I sometimes would take some straight to Sierra Leone," he added.
Asked by prosecutor Nicholas Koumjian if he ever saw diamonds, Marzah replied: "Many times. I escorted diamonds to Charles Taylor. He himself can tell you that if he tells the truth," he said.
He told the court he had personally brought some 10 to 15 consignments of diamonds to Taylor.
He recalled one diamond in particular that was around five centimetres (two inches) in diameter.
"At that time, we called (it) father'. When he took it along, Charles Taylor was impressed," Marzah said.
Here is a video of some of these savages atrocities in Liberia....
Taylor, 59, is accused of arming, training and controlling the Revolutionary United Front (RUF) rebels in Sierra Leone in exchange for still-unknown amounts of diamonds.
Around 120,000 people were killed in the conflict, and thousands more were raped and mutilated with rebels cutting off arms, legs, ears or noses.