Because of the increase of evidence of blood stains, that have been washed or cleaned in an attempt to
mask the analysis of DNA profiles, there is also an increase in the use of presumptive tests on samples
sent to laboratories. Some of the presumptive tests, used to identify blood and semen stains, could
potentially affect the recovery of high molecular weight DNA from the samples, or extinguish them,
especially those already present in small quantities. After the presumptive tests, often these samples are
discarded. This study aimed to examine the possibility of obtaining a DNA profile from samples
submitted for presumptive testing and cleaned with bleaches with and without chlorine. Two different
protocols were conducted: (a) A unique sample of human blood in natura (5 mL), already typed through
the DNA techniques with the genetic profile previously known (control), was distributed onto cotton
fabrics and dried at room temperature. Four samples of fabric were macerated in saline solution and
Coombs serum and then stored for three months (room temperature and freezer 20 8C). (b) Another
sample of human blood, type A, in natura, already typed through the techniques of DNA (control) was
used. Aliquots of 200 mL were distributed in: cotton, denim and synthetic fabric. The samples were dried
at room temperature for 24 h. The blood stains in those fabrics (cotton, denim and synthetic) were then
divided into three groups: unwashed, cleaned with chlorine bleach and cleaned with chlorine bleach and
soap powder. The samples were again dried at room temperature for 24 h, before the use of luminol. The
DNA were extracted with Chelex 100 and amplified with the Identifiler Kit (Applied Biosystems). The
blood stains exposed to saline and Coombs serum had DNA profiles consistent with untreated samples
(controls). This result shows that the experts should keep and store the samples treated with saline and
Coombs serum for future DNA confrontation when necessary. Also discussed in this paper the pattern of
blood stains after washing with bleaching solutions, as well as the quantity of DNA obtained from these
samples.