presenciase
-I witnessed
The word presenciase is the imperfect subjunctive form of presenciar in the first person singular. There are other translations for this conjugation.
See the full presenciar conjugation

presenciar

Si alguien presenciase un atraco, ¿no crees que habría dado aviso?
If someone interrupted a robbery, don't you think they'd have called it in?
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