In the 1730s there was a sudden craze whereby a lot of burglaries took place in churches, often accompanied by a few brutal robberies on priests.
Many suspects of petty crimes often also confessed to these heavier crimes because of the torture they had to undergo. In addition, they were forced to mention names of accomplices. One suspect said that they had to pledge an oath to the devil on Duivelsberg (which means devil hill). In this respect, black magic was first introduced as "evidence" in the trials due to the forced confessions under torture.

On February 22 1771, Joseph Keyser named “the barber surgeon from ’s-Hertogenrade” as an accomplice in a voluntary statement. Apparently, Keyser did not know his real name. Nevertheless, he was in doubt about it: it could have been him, but he wasn’t sure. Merely based on this statement, a prosecution could not be filed for Kerckhoffs.

However, after Keyser’s statement, the tribunal has attempted to steer the statements of other convicts into that direction. For instance, Peter Muller mentioned Kerckhoffs as one of the people present at the robberies and added that he was riding his horse. In addition, Hendrik Steyns passed out while enduring the torture, because he was unable to name the barber surgeon, which was interpreted by the court as purposeful concealment of information about the identity of the gangleader.

In July and August of the year 1771, the defendants had to talk about their leader. The court would especially ask who was riding a horse during the robberies. Strikingly, some claimed that they saw five men riding a horse.

Joseph’s brother Balthus Kerckhoffs owned a busy cobbler’s store in Merkstein where people would travel to from remote places to have their shoes mended. Balthus was known in the region, but was now named as an accomplice. He was subsequently heavily tortured and falsely confessed to the crimes which he was accused of. He then revoked his confessions, but was subjected to torture again and consequently died in his cell. Afterwards, Muller named Balthus as one of the takers of the oaths in the chapels and as one of their leaders. This leads to the question whether it was out of frustration because they weren’t able to find out more about Balthus that the court turned to his brother as one of the main suspects.

Joseph Kerckhoffs (Dutch) or Kirchhoffs (German) was born in ’s-Hertogenrade on October 24, 1724 as the youngest of six siblings. In 1743, he obtained his certificate as a barber surgeon, a healer that –as opposed to a physician – has no university degree. These barber surgeons had usually learned about the profession from someone else. They called themselves “barber surgeons”, because they also specialized in the activities of a barber such as shaving beards.

In that same year, during the War of the Austrian Succession, he enlisted in the Austrian army. He left the army in 1752 after he found out that his hometown lost their barber surgeon. He contacted his acquaintances and asked a Jesuit, the almoner of the emperor’s army in Brussels, to put in a word for him with abbot Frabicius, the prelate in Kloosterrade.

Kerckhoffs was also acquainted with Joseph of Grupello, the only son of sculpturist Gabriel whose daughter was married to Peter Casper Poyck, schout (local officer appointed to perform administrative tasks) of Merkstein and the direct successor of his much older brother Balthus. The acquaintances in the clerical social circles recommended Kerckhoffs as a chaste man who had kept himself far away from the perversities in the army.

He was hired. Joseph returned to his hometown after ten years and settled down in the house of his uncle Hendruk Kerckhoffs. Since the beginning of 1753, Joseph became the town’s barber surgeon and of those in the surrounding towns, such as Ubach where he took care of the ill and where he performed autopsies.

In 1759, he married Elisabeth Mans. Their marriage was blessed with six children. During the Bokkenrijder trials – which were executed in his town’s castle –he knew his name came up as one of accomplices of the gang, but he never felt comforted in his innocence. His connection with the Bokkenrijders has never been proven other than in statements about possible suspects that were conducted under torture. Many of these names only appeared in these forced statements and never came up in tangible evidence. Because of the heavy torture, the suspects would take over the suggestions made by the court.

However, Kerckhoffs was an exception to the rule, since Bokkenrijders were usually poor wretches, beggars and tramps.

In the early morning of August 14, 1771, the barber surgeon went to the Church of St. Mary like usually in order to attend the early mass service. When he left the church, he was arrested under the suspicion of being the leader of the Bokkenrijders gang and he was brought to the castle of ’s-Hertogenrade. He called on priests as witnesses in favor of him.

His first questioning under torture occurred on October 10. Kerckhoffs went through all the stages of torture but did not confess to anything. He endured the most gruesome torture. On the next day, the torture was repeated. Kerckhoffs was completely debilitated and the torture had to be stopped. Nevertheless, his interrogators were convinced of his guilt.

On November 12, Joseph was tortured again for three consecutive days. On November 14, he passed out after hanging on the strappado for too long and he had to be taken down on the order of a physician.

After Kerckhoffs’ arrest, the trial against his fellow convicts continued. They were forced to identify the barber surgeon as their leader and attest to the “fact” that Kerckhoffs accompanied them on his horse during their raids.

In the spring of 1772, Kerckhoffs was tortured again. Despite the inhuman pains he had to endure, he did not confess to any of the accusations against him. The judges were taken aback by this and saw this as evidence that this must be the work of Satan. Since they couldn’t risk a miscarriage of justice and releasing Kerckhoffs. Therefore, they read his verdict which was death penalty without any confessions on May 4, 1977. This was unparalleled before. Additionally, he received death penalty with the rare reference that he were to be tortured once again until “the revelation of his accomplices”.

On May 6, 1772 the death penalty verdict was disclosed to Kerckhoffs and he was tortured for the last time. Lieutenant de Limpens, the schout of Kerkrade, the priest of ’s-Hertogenrade and two Jesuits were present. Court clerk Cox read his verdict out loud. On that same day, although he was tortured again, Kerckhoffs did not make any confessions. Therefore, on the next day, the court pulled out all the stops and tortured him again in the most gruesome way thinkable. According to court documents, they laid fire under the soles of his feet, he had to go on the strappado again and also the torture horse was present again. Kerckhoffs remained insensitive to the allegations. He then said the famous words in German: Meine Herren! Ist Ihnen nu Genüge geschehen? Wo nicht, so möget Ihr meinem Leib in Stücke zerreissen und die einzelnen Teile ins Feuer werfen lassen. Darum sollt Ihr aber noch nichts weiter aus mir herausbringen!”

The court then tried their last method to make him confess. They called on the Jesuit Joseph Zunder from Koblenz, who was in charge of the Sacrament of Penance in the Holy Mary Monastery in Aachen, which – according to Sleinada – was the only one who wrote about the last hours of Kerckhoffs’ life. The Jesuit had children in ’s-Hertogenrade pray for Kerckhoffs during his torture.

Jesuit Zunder started to prepare Kerckhoffs for his death on May 9 and continued on the following day. He tried to make Kerckhoffs confess, but he kept persisting in his innocence.

On May 11, Jesuit Zunder accompanied Kerckhoffs to the gallows. Lieutenant de Limpens from ’s-Hertogenrade went –according to Sleinada - to Kerckhoffs’ cell that morning and swore that he would have all witness reports against Kerckhoffs destroyed if they were proven to be untrue. However, all of them stuck to their former statements. At 11 am, Joseph Kerckhoffs ascended the ladder of the gallows on Beckenberg near ’s-Hertogenrade. A large crowd had gathered in large numbers which was unprecedented according to the historian. Joseph Kerckhoffs was found guilty as an accomplice of a gang of thieves and burglars by night, as well as nine crimes, nothing about a godless oath or church robberies. He was convicted to be hanged and be tied to a chain afterwards. He was not allowed to be buried. His body had to decay while it was still on the robe. His death caused many controversies.