The important points are:
States can commit crimes.
In the narrowest sense of the word, if a government minister - or a civil servant, or a soldier - commits fraud or assault while carrying out his/her duties, that could be seen as a 'state crime' in the same way that a crime committed on business premises could be called a 'white collar crime'. You can also define 'state crime' as a breach of the laws which governments commit themselves to obey, e.g. international human rights laws or trade agreements: strictly speaking, a government permitting its country's fishing fleet to fish another country's waters is committing a state crime.
The International State Crime Initiative uses a different (and more useful) definition, based on "organisational deviance" leading to "human rights violations". In other words, "organisational deviance" (collective wrongdoing), within a government organisation, has led to people being harmed. State crime doesn't have to be illegal (under national or international law); it needs to breach human rights, and it needs to have to have some kind of organisational backing (an individual soldier going rogue can't commit state crime).
Most terrorists aren't 'terrorists'.
Changing the subject slightly, there's a big problem with the generally-accepted academic definitions of 'terrorism'. There's a consensus right across the literature: terrorism means indiscriminate attacks on civilians and 'symbolic' targets, carried out with the aim of inducing terror and changing political behaviour - by intimidating the general public and/or by influencing the government. Some terrorist groups fit the bill some of the time: Al-Qaida is only the most obvious example. But there wasn't very much that was 'terrorist' (according to the textbook definition) about the activities of the Red Brigades in Italy or the Provisional IRA in Ireland or the Palestine Liberation Organisation. "Armed struggle" groups don't bomb newspaper offices or murder police officers or assassinate politicians because they want to terrorise the general public, or even because they want to intimidate journalists and police officers and politicians; they do it because they believe they're fighting a war and those targets represent their enemies.
If the textbook definition of 'terrorism' doesn't describe actual flesh-and-blood terrorists, what does it describe?
States can use terror tactics.
In political discourse, the word 'terror' goes back to the French Revolution. The first 'Terror' was an eleven-month clampdown on political opponents, involving mass executions of enemies of the regime; between September 1793 and the following July, tens of thousands died on the guillotine. Subsequently the word 'terror' was widely used to describe indiscriminate killing by governments, particularly in the aftermath of an attempted revolution - the Hungarian "White Terror" of 1919-21 is only one example. When the development of military aircraft permitted it, "terror bombing" was carried out in World War II (Dresden, Hamburg), during the Spanish Civil War (Guernica) and in Britain's colonies (Mesopotamia, a.k.a. Iraq).
There's no textbook definition for "terror bombing" - or "state terror" - but when you look at the textbook criteria for terrorism (indiscriminate attacks on civilians and 'symbolic' targets, carried out with the aim of inducing terror and changing political behaviour) both Dresden and Guernica seem to fit quite well.
Organisational deviance needs a permissive environment.
It's not unknown for a government to be led by somebody who openly flouts the law, laughs at international agreements on human rights and generally acts like Dr Evil. It's not unknown, but it is very, very unusual. When business executives commit crimes they usually reach the point of breaking the law through many small steps - turning a blind eye, making excuses, blaming the competition - and governments are no different. When government ministers commit state crimes, they usually believe that they have to commit them. Or that it's OK this once. Or that the end justifies the means. Or that another government would do it if they didn't...
In business, a tightly-regulated company - with lots of paperwork and regular visits from the auditors - is an environment where a culture of wrongdoing is unlikely to develop. An unregulated company, running on personal relationships and word-of-mouth instructions, is a 'permissive environment' for organisational deviance: a place where a culture of wrongdoing can take root and grow. It's the same with governments: some of them are permissive environments for organisational deviance, some aren't. A government which acts on the basis that the head of government is above the law; or that there's a war on (when there isn't); or that there's a pressing emergency threatening the very life of the nation itself... any government like that is a very permissive environment for organisational deviance, up to and including state terror.
To sum up: governments are much more likely to use terror than most 'terrorists'. State terror is a state crime (in war it's a war crime), and as such it can only happen on the basis of 'organisational deviance' - a phrase which here means 'a government collectively thinking that it's above the law'. A frequent setting for organisational deviance in government is... counter-terrorism.
