Early one morning in 1981, I arrived at the middle school where I taught in Tehran and was informed by two guards from the notorious Evin prison that one of our students had been arrested and would not be returning to school.

I knew that his father was a drug dealer, and supposed that he had been arrested on similar charges. It was the height of the post-revolutionary struggle between Iran's revolutionary democratic front led by then-president Abolhassan Banisadr, and the dictatorial front led by the Islamic Republican party and its allies. A few months later, Banisadr was ousted in a coup and I was fired from my teaching post.

Later on I learnt that on the same day my former student had been released and recruited as a guard in the same prison. I also learnt from his grandmother that he had not been involved with drugs, but had raped his sister and made her pregnant. At the time, stories of women and girls being raped in prison became so rife that Ayatollah Montazeri sent a team to investigate. They only verified the rumours. Male prison officers – many of them psychotic like my former student – were tasked to rape women, and extensively; one was even nicknamed "hamishe daamaad" (the forever groom).

In other words, rape is nothing new to this regime, which even now tries in vain to hide itself behind Islam. However, after last June's uprising, we are observing the emergence of a more widespread form of rape, and one that is also extended to men. This is not to say that it did not exist before, but now we are observing its systematic use. There is little public information about this to date.

Abuses at Kahrizak prison, which came to be known as Iran's Abu Ghraib, were exposed only because Mohsen Rooh-al-Amini, the son of a well-established conservative figure, was killed under torture. The regime was forced to close the prison and, later in August 2009, Ayatollah Karubi issued a statement saying, among other things, that some prisoners had been raped. After such exposure, one might have thought the regime would stop this brutal form of torture against its opponents. But victims and witnesses have continued to report its continuation. A few weeks ago, for example, revolutionary guards arrested a group of women that has gathered every Friday night in Laleh Park to protest the detention of their children.

While in prison herself, one mother revealed that she saw a teenage boy begging a judge not to sent him back to solitary confinement. When the judge asked why, the boy replied, "because they keep raping me". Two months ago, my friend's son was arrested in a demonstration, and had to wage the fight of his life to prevent being raped by the guards in the car. And on 12 February, Fatemeh Karubi, wife of Ayatollah Karubi, wrote an open letter to Khamenei detailing the arrest of her 38-year-old son when his father's car was attacked at a demonstration on the 31st anniversary of the 1979 revolution. She described how her son was viciously abused, both physically and verbally, in a mosque. The guards threatened to rape him.

Why, despite its public exposure, does this regime continue to use rape and the threat of rape as weapons against its opponents, women and men alike? The question has to be understood within its cultural context. The regime knows that killing an opponent will make a martyr of her or him, and may even encourage others to join the struggle. Rape, however, can have devastating effects not only on an individual but on political morale as well. The regime believes that society believes that no one can become a hero for being raped. Within this context it is easier to risk one's life for what one believes in, but difficult to join a protest knowing one might be raped. Also, even this regime finds it difficult to hide the murders of its opponents, but it can often neutralise a dissenter with rape, as most victims are too traumatised and ashamed to make this public.

However, it is not at all clear that this threat of shame will remain powerful. Throughout this revolutionary struggle, we are observing astonishing shifts in cultural norms and values, especially in gender relations and in opposition to elements of patriarchy. We saw how the regime's efforts to humiliate a student by publishing a photograph of him dressed in woman's clothes fell flat; in just hours, thousands of other men snapped pictures of themselves in female dress, and published them on the internet to express solidarity. Of course, centuries of patriarchal values and relationships will not vanish overnight. But Iranian society is learning fast that whoever suffers as a result of their struggle against the country's most barbaric regime in the last two centuries has to be seen as a hero.

This regime is now fighting for survival, and has no red line left to cross. Since Ahmadinejad's appointment to president and the encroachment of the Revolutionary Guard's generals into the state and the economy, it can safely be considered a military-financial mafia. And like any other form of totalitarian state, it has sought and trained the most dehumanised individuals to become decisive, efficient and effective weapons in this struggle.

They are, of course, culpable. But others must be brought to account. Khamenei, as the supreme leader with absolute power over – according to his ideologues like Ayatollah Mesbah Yazdi – every Iranian person's life, property and honour, and as the person who openly declared war on protestors after the election, bears ultimate responsibility for these crimes. He has already been accused of murdering his opponents into submission by a German court in the Mykonos trial, and has received numerous letters calling him to account for other crimes and abuses.

Fatemeh Karubi's letter is only the latest public example. Human rights organisations also have ample evidence of all sorts of crimes committed against the Iranian people by this regime, and we expect them to soon begin a process of establishing an international court in which Khamenei can be indicted for committing crimes against humanity.