German born individual, emigrated to US, accumulated wealth, returned to Germany upon retirement and died in Germany. Are his US assets subject to Germany's inheritance taxes.
He had become incompetent in Germany and his son, in the US, had sought protection of his assets through a US Probate Court. Son was Conservator. All US assets are titled in name of Conservator. Local Probate Court (in Connecticut) seems to have jurisdiction to open an estate and probate these assets (less than $500K). Seems as though there would be no US Estate Tax.

Any Estate taxes due would be determined by the state law the assets are located in. Some states have inheritance taxes... some don't.