Prosecutors charge that the 30-year-old, who was not named by authorities, murdered the woman in front of two of her children because she had turned her back on the Islamic faith.
The Muslim man allegedly used a 20-centimetre bladed knife to slash and stab the Afghan woman 16 times outside a supermarket in the southern city of Prien on Chiemsee lake on April 29th last year.
The case came at a time when the German public is torn over a mass influx of more than one million refugees and migrants since 2015, many from conflict-torn Syria, Iraq and Afghanistan.
The 38-year-old woman had earlier asked the man whether he wanted to convert too, a request that was "irreconcilable with his Muslim faith," prosecutors told the court in the city of Traunstein.
Two of the woman's children, aged five and 11, watched as the man allegedly killed their mother. Her two other children are adults.
Passers-by tried to stop the attacker by hurling a shopping trolley at him.
After his arrest, the man claimed he had acted out of frustration about his looming deportation as a rejected asylum seeker.
He was initially held in a psychiatric ward for about three months and then transferred to standard pre-trial detention.
The court has scheduled four days of hearings.
Homicide carries a life term under German law, although convicts are usually released after 15 years.