The pair, who pleaded guilty to the robbery but denied hurting Gsell, were found guilty of causing his death and each sentenced to eleven years of prison.
In January 2003, they broke into Gsell's villa with axes and injured the 76-year-old so badly that he died soon afterwards, presiding judge Gerhard Neuhof found.
"By thoughtlessly employing violence the accused brought about the death of their victim," Neuhof said.
In the judgement, the court found that the men had planned to attack Gsell from the beginning.
They struck him several times with their fists and with the axes so that they would be undisturbed while looting the property.
The judges rejected the men's claims not to have hurt the doctor, saying that he himself gave a believable description of their behaviour shortly afterwards.
Wife planned car insurance fraud
Also mentioned in the judgement were Gsell's widow Tatjana, two car smugglers and a former state prosecutor.
Investigators believe that the robbery was linked to a plan by this group to steal Gsell's limousine and claim the insurance payout.
"There was certainly a plan and relevant conversations around car smuggling," Neuhof said.
While it is unknown how far the group had progressed with their plan, the court determined that none of them was guilty of involvement in Gsell's fatal wounding.