Phenolphthalein False-Positive Reactions from Legume Root Nodules

Daniel Petersen, Frank Kovacs

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Presumptive tests for blood play a critical role in the examination of physical evidence and in the determination of subsequent analysis. The catalytic power of hemoglobin allows colorimetric reactions employing phenolphthalein (Kastle-Meyer test) to indicate "whether" blood is present. Consequently, DNA profiles extracted from phenolphthalein-positive stains are presumed to be from blood on the evidentiary item and can lead to the identification of "whose" blood is present. Crushed nodules from a variety of legumes yielded phenolphthalein false-positive reactions that were indistinguishable from true bloodstains both in color quality and in developmental time frame. Clothing and other materials stained by nodules also yielded phenolphthalein false-positive reactivity for several years after nodule exposure. Nodules from leguminous plants contain a protein (leghemoglobin) which is structurally and functionally similar to hemoglobin. Testing of purified leghemoglobin confirmed this protein as a source of phenolphthalein reactivity. A scenario is presented showing how the presence of leghemoglobin from nodule staining can mislead investigators.

Original languageEnglish (US)
Pages (from-to)481-484
Number of pages4
JournalJournal of Forensic Sciences
Issue number2
StatePublished - Mar 2014
Externally publishedYes


  • Blood test
  • Bloodstain
  • DNA extraction
  • DNA typing
  • False-positive
  • Forensic science
  • Hemastix
  • Hemoglobin
  • Kastle-Meyer
  • Leghemoglobin
  • Legume
  • Phenolphthalein
  • Polymerase chain reaction
  • Presumptive
  • Short tandem repeats

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Genetics


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