The trial for the man who is alleged to have shot four police officers in a siege near Kawerau has begun in Hamilton's High Court.

Rhys Warren, 28, has been charged with two counts of attempted murder, one count of wounding with intent to cause grievous bodily harm and three charges of using a firearm on a law enforcement officer, for an incident in March last year.

One of the officers was shot in the head and suffered a serious brain injury.

Warren is representing himself and has said at past court appearances that the Crown have no authority to try him.

The jury of eight women and four men have just been selected.