This is the 6162nd most frequent Korean word.
수사하는
"Investigating" or "conducting an investigation."
In this sentence, '수사하는' modifies the noun '형사 (detective)' to describe the detective's action of investigating a case.
그는 사건을 수사하는 형사입니다.
He is a detective investigating the case.
Here, '수사하는' modifies the noun '기술 (techniques)' to specify the investigative techniques being mentioned.
수사하는 기술이 점점 더 발전하고 있습니다.
The techniques used for investigations are continually advancing.
In this usage, '수사하는' is describing '사람들 (people)' as those engaging in the act of investigation.