If we find a dead female, how can we find out if she is Muslim?

(Fatwa: 254/55=TL/1430)

If there is special dress worn only by Muslim women and the dead woman was found wearing Muslim clothing then she will be considered Muslim, she will be given bath and the salah of her Janazah (funeral) will be offered. But, if there is no sign of her being a Muslim, then she will be considered Muslim if found in Muslim locality and will be considered non-Muslim if found in non-Muslim locality:

ولو لم یدر أ مسلم أم کافر ولاعلامۃ (فإن في دارنا الخ ) أفاد بذكر التفصيل في المكان بعد انتفاء العلامة أن العلامة مقدمة وعند فقدها يعتبر المكان في الصحيح لأنه يحصل به غلبة الظن

Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband