A prominent Israeli peace activist is expected to be sentenced to several months in jail tomorrow in a high-profile prosecution which began after he tried to stop the demolition of Palestinian homes near a Jewish settlement in the occupied West Bank.

Although activists who challenge the Israeli occupation are often arrested or detained for short periods, Ezra Nawi, a plumber from Jerusalem, is expecting a sentence of up to 18 months. He said he would lodge an immediate appeal, which may keep him out of prison initially, but it is likely he will be jailed within weeks.

In March he was convicted by a judge at a Jerusalem court of taking part in a riot and assaulting a police officer, charges he denies. The incident happened when the Israeli military sent bulldozers to demolish Palestinian shacks near the settlement of Carmel, close to Hebron, in February 2007.

Nawi, who is in his 50s, has worked with vulnerable Palestinian families in the hills around Hebron for at least eight years. But he is an unusual figure, even among Israel's shrinking circle of leftwing activists.

Born to a Jewish Iraqi family from Basra, he speaks Arabic and lives on the modest earnings of his plumbing work, not a typical story for leftwing activists. Instead, he said, most Israelis from his Middle Eastern background have strong rightwing views and often serve in the border police force that arrested him in the first place.

He is also gay and has frequently faced homophobic taunts from Israeli police, soldiers and settlers in Hebron who, by now, are used to his regular presence in the area. He is motivated, he says, by a will to resist the "dehumanisation" of the Palestinians.

"I have seen the checkpoints, the barriers. I've seen everything with my own eyes and I think any decent person cannot sit indifferent to this. It is beyond the issue of Jews and Arabs," he said. "Here everybody sees it, but not everybody refers to it … the settlement is a few metres from them on their land, and they are in heartbreaking poverty, and then the police come to demolish the house, and this is legal? It's beyond politics."

His trial has sparked a broad campaign of support from academics, musicians and artists. "You have here the whole misery and cruelty of the occupation in a nutshell," David Shulman, a Hebrew University professor and activist with the Israeli-Palestinian peace group Ta'ayush, wrote in the Ha'aretz newspaper.

"Inside the occupied Palestinian territories is a shadow state where the only real law is the law of the gun, where land is being taken away from its rightful owners every day, and where the very few who stand up to protest, without violence, like Ezra Nawi, are sent to prison."

Another Hebrew University academic and peace activist, Amiel Vardi, who teaches classics, said: "I don't know of anyone as dedicated as Ezra." Vardi, too, said Nawi was different from most. "We are others. Even for those who work with us for years and perhaps understand more or less what we are doing, we are still others," he said. "Not Ezra. Ezra is accepted as a human being, meaning they both belong to the same group. He is not so much of an other."

The case against him relies on the testimony of two border police officers who allege Nawi punched them during the demolition. The demolition was videoed, but the alleged incident took place inside one of the shacks and is not caught on film. Nawi admits he shouted, protested and lay in front of the bulldozer, but insists he is committed to non-violence and did not strike the officers.

Neither officer mentioned any punch in their initial statements, but Judge Eilata Ziskind said their testimonies were still reliable. In her verdict she said: "Freedom of speech is not the freedom to act in an inciting manner or to take steps to prevent or disturb police work … freedom of speech is not the permission to be unruly and certainly not to use violence."

Once he has been arrested and cuffed, the video shows Nawi sitting in the back of a border police van as the officers laugh at him. He tells them: "Yes, I was also a soldier, but I didn't demolish houses. There's a big difference. The only thing that will be left here is hatred."