Cold case

New technological methods developed after the crime was committed can be used on the surviving evidence for analysis often with conclusive results.

Typically, cold cases are violent and other major felony crimes, such as murder and rape, which—unlike unsolved minor crimes—are generally not subject to a statute of limitations.

Eventually, the alibi is disproved, the witnesses recanted their statements or advances in forensics helped bring the subjects to justice.

With the advent of and improvements to DNA testing/DNA profiling and other forensics technology, many cold cases are being re-opened and prosecuted.

Similarly, the Zodiac Killer has been studied extensively for almost 50 years, with numerous suspects discussed and debated.

The perpetrators of the Wall Street bombing of 1920 have never been positively identified, though the Galleanists, a group of Italian anarchists, are widely believed to have planned the explosion.