 Records from the Auburn Public Library , when subpoenaed , showed that Nickell had checked out numerous books about poisons , including Human Poisonings from Native and Cultivated Plants and Deadly Harvest . The former was marked as overdue in library records , indicating that Nickell had borrowed but never returned it . The FBI identified Nickell 's fingerprints on cyanide @-@ related pages of a number of the works she had checked out from the library in this period . 
