1、The crime was committed in an unwitnessed alley, making it difficult for detectives to gather evidence.
犯罪行为发生在一个没有人目击的小巷中,使得侦探们很难收集证据。
2、Without any eyewitnesses, the accident remains unwitnessed and the cause is still unknown.
由于没有任何目击者,这起事故仍然没有人目睹,并且原因仍然不明。