Historical clue formulations

• Bottle marked with a skull and crossbones — 2022-01-23
• Downfall in many an Agatha Christie novel — 2020-11-08
• One of the nine weapons in 2008's expanded version of Clue — 2019-07-06
• Staple of Agatha Christie mysteries — 2014-05-06
• Murder method in Christie's "A Pocket Full of Rye" — 2010-02-10
• Exterminator's option — 2008-03-23
• Arrow application — 2004-10-29
• Skull-and-crossbones stuff — 2001-06-26
• Kind of pen — 1999-10-22
• Pesticide — 1997-12-14
• Corrupt — 1997-04-19