Last night I googled "Luminol appeal" and found lots of court opinions on the admissability of Luminol tests in different states across the US. In most states luminol tests are admissable as a "presumptive test" and it is up to the jury to determine the weight of the evidence. From wikipedia:
"In medical and forensic science, a presumptive test is an analysis of a sample which establishes either:
1.The sample is definitely not a certain substance
2.The sample probably is the substance"
It does appear that different states have ruled somewhat differently on the question:
There is the case of Palmer v. State from Arkansas which held that
"The mere presence of human blood by luminol testing
without factors which relate that evidence to the crime is not
admissible; luminol tests done without follow-up procedures are
unreliable to prove the presence of human blood or that the substance
causing the reaction was related to the alleged crime.
2. APPEAL & ERROR - PROOF PREJUDICIAL - ERROR FOUND. - Where
the state's proof concerning luminol, including photographs of the
bedroom, was weighed against the evidence generally, which evidence
failed to show that the test results were related to human blood
related to the crime, the supreme court found prejudice in the admission
of the luminol results."
http://opinions.aoc.arkansas.gov/weblink8/0/doc/109012/Electronic.aspx
I don't know if there are subsequent cases in Arkansas overturning this opinion. see also
http://ar.findacase.com/research/wfrmDocViewer.aspx/xq/fac.19930125_0042592.AR.htm/qx