This is the 5786th most frequent Polish word.
zabójstwem
"Zabójstwem" means "murder" or "homicide" in English.
Here, 'zabójstwa' uses the genitive case to describe the object of the investigation, showing possession or relation to an act of killing.
Policja prowadzi śledztwo w sprawie zabójstwa.
The police are conducting an investigation into the murder.
'Zabójstwo' in the accusative case indicates the act itself, describing the crime committed.
Był zamieszany w zabójstwo znanego polityka.
He was involved in the murder of a well-known politician.
'Zabójstwa' again applies the genitive case, emphasizing the nature of the crime involved in the accusation.