"My worst injury was in my face. I felt like a ball of fire spinning inside my face, all of my teeth flew out," she told the panel led by former South African judge Richard Goldstone.
"What was my sin, what was my crime? I'm a Jewish physician in Ashkelon. I studied medicine to help people. I didn't care if they were from Gaza from anywhere in the world," said the gynaecologist, who treated Palestinian women before access was blocked.
"What was my crime, what did I do wrong, why did I wind up in this situation?"
"I'm just an ordinary citizen. I never played a role in any war. I didn't take part in any battles, I don't know what battles are about, I have no understanding. I want you to understand that," Sidera added, speaking through an interpreter whose voice started to tremble.
The gynaecologist carries facial scars after undergoing six operations and still has a four-centimetre piece of shrapnel lodged near her spine.
The two-day session in Geneva follows a first set of hearings in the Gaza Strip late last month that was dominated by gruesome testimony of Palestinians trapped under Israeli shelling during the 22-day offensive.
About 1,400 Palestinians and 13 Israelis were killed during the fighting.
Much of the Israeli testimony Monday revolved around indirect accounts of psychological trauma built up over years of rocket attacks by Palestinian militants, mainly on the Israeli towns of Sderot and Ashkelon, the closest to the Gaza Strip.
"This is an important but small part of our investigation," Goldstone said of the hearings.
The mission has a broad scope to investigate alleged violations committed by all sides around the offensive in December and January, which Israel said was aimed at stemming rocket fire from the Hamas-ruled enclave.
Forty-six missiles hit Ashkelon in 2008 and 25 so far this year, exploding in shopping malls, sports centres and a school, according to mayor Benny Vaknin.
Ofer Shumar, a human rights lecturer in Sderot who provided social assistance during attacks, underlined the trauma that has paralysed many of those who stayed in the town and couldn't afford to move out.
He also pointed to "major fury, such anger in them.
"The real issue is the 30 percent who have long term effects, especially young people," said Rony Berger of Natal, an Israeli center providing assistance to trauma victims.
Shumar sought to explain, dispassionately, another underlying wound.
"Israeli's society's problem is that because of the conflict it feels itself to be a victim and to a large extent that's justified," he told the panel.
"It's very difficult for Israeli society to move and to also see the other side and understand that the other side is a victim too. That's the greatest tragedy of the conflict and it's terribly difficult to overcome."
The public session at the UN's human rights headquarters in Switzerland is meant to allow those who were unable to travel to Gaza to provide public testimony.
Israel also refused to allow the mission access to its territory while some were not allowed to leave the West Bank to testify, Goldstone said.
One of them, a Palestinian human rights activist in Ramallah, tried over a video link to outline the disruption wrought by travel restrictions and barriers on the everyday lives of Palestinians in the territories.
"They say I'm a danger for security. I don't know if I'm more dangerous in Geneva or in Ramallah. My personal view is that it's a form of punishment," he added as the link broke up.
The hearings continue Tuesday.