O'Connor, 41, was arrested by the Israeli secret police, Shin Bet, after planting olive tree seedlings in front of the illegal separation wall in the West Bank town of Biddu on 25 January.
He came to the West Bank last month to volunteer with the International Solidarity Movement (ISM), a peace group consisting of Palestinian and international activists working to raise awareness of the Palestinian situation.
In addition to participating in non-violent protests against the separation wall, he served as an unofficial elections monitor, observing Israeli restrictions on some 118,000 Palestinians in occupied East Jerusalem as they attempted to vote in Palestinian presidential elections in January.
O'Connor, a dual US and Irish citizen, was initially denied entry into Israel last year based on secret evidence that neither he nor his lawyer were allowed to see, and which has still not been revealed to him.
He later returned to the West Bank on his Irish passport, something Israeli authorities say he should not have done, and on which they will likely base their case against him, according to his lawyer Gabby Lasky.
Support international law
The Israeli government often accuses human-rights workers and peace activists such as those belonging to ISM of "meddling", being "naive", disturbing the work of occupation soldiers and providing "cover" for "Palestinian terrorists".
"[It is] ridiculous and is only propagated by those who seek to discredit the message of thousands of principled volunteers from around the world who are bearing witness to the cruelty of occupation and working non-violently to end it"
The ISM on Israeli charges that it covers 'Palestinian terrorists'
In a statement on their website, the group says the charge is "ridiculous and is only propagated by those who seek to discredit the message of thousands of principled volunteers from around the world who are bearing witness to the cruelty of occupation and working non-violently to end it".
In an interview with Aljazeera.net from his Ramle cell, O'Connor said of the meddling charge: "It's all of our responsibility to support international law and human rights, and since our governments are failing to do that, then citizens have to take that responsibility themselves."
He added that after nine days in prison, he was starting to get a sense of what life is like for Palestinians living under occupation in the West Bank and Gaza Strip.
"I'm imprisoned, as are the Palestinian people. But imprisonment will not silence opposition."
Last July, International Court of Justice based in The Hague ruled the separation wall illegal by standards of international law, and recommended its demolition.
However, O'Connor said Tel Aviv has done nothing but harass and arrest Palestinian, Israeli, and international activists who peacefully protest against the wall's construction.
The ICJ also made clear that all signatories to the Fourth Geneva Convention had an obligation to enforce Israel's compliance with international humanitarian law.
The American activist said his arrest "proves" that the Israeli government is systemically attempting to prevent human rights workers and supporters of Palestinian rights from entering the occupied territories and "witnessing what's happening".
"[They] are trying to crush legitimate opposition and non-violent opposition to their policies that ultimately has more of a chance at succeeding," he said.
"By attempting to block people like me they are violating their obligations under international law."
Under the Fourth Geneva Convention, Israel is required to allow humanitarian access to the territories it occupies.
Lasky, lawyer for O'Connor, said she was appealing the Israeli decision to deport him, and - in what would be a precedent setting case according to Israeli legal sources - demanding that Israel declassify the Kafkaesque blacklist on which many human-rights activists find themselves placed.
"It's all of our responsibility to support international law and human rights, and since our governments are failing to do that, then citizens have to take that responsibility themselves"
Patrick O'Connor, US peace activist jailed by Israel
"We don't have any possibility to see those lists or to know how you can erase yourself form those lists, or what the criteria are that make you get on them.
"So this time we are asking to see the list, and the criteria used to create it. We want to show this [arrest] is part of a pattern," said Lasky, who is attaching the names and cases of more than 50 non-violent activists who have been detained or deported while working in Israel.
Lasky said deporting O'Connor would not only hurt Palestinians but Israel, too.
"Patrick has been involved in human rights and humanitarian work with children for many years. I think not only the Palestinians are losing but also Israel is losing when he is not allowed to stay, because these people are doing work that Israel should be doing," the lawyer said.
When questioned about O'Connor's case and about the accusation that they systemically detain and deport foreign activists, an Interior Ministry spokesperson said O'Connor was refused entry last year based on the "recommendation of the security bodies of Israel".
It referred Aljazeera.net to the Prime Minister's Office which oversees the issue, for an explanation, but the office said it had no comment on the matter.
O'Connor has worked for 11 years with US non-governmental organisations managing multi-million dollar humanitarian aid programmes in Morocco, Egypt, Mali, and the Gaza Strip.
He was not allowed to enter Israel from Egypt to testify at his own hearing last year in Beer Sheva, even though he agreed to be handcuffed and put under Israeli police guard.
His is the latest in a string of Israeli arrests, deportations, and general harassment of human rights workers in general, and ISM volunteers in particular, serving in Israel and the occupied Palestinian territories.