Imperfect science can be described as the scientific study of a research/field that is not complete or is characterized with a number of faults. While there are many scientific research fields or focus that fall under this category (because scientists are constantly seeking to improve existing knowledge of various scientific field), let's limit our scope to DNA evidence analysis.
DNA evidence testing for instance is very expensive which makes it difficult (in most cases) for victims to request for it in cases of crime (except requested by the government). For instance, if a killing that involves a struggle was done in a small neighborhood of about a 100 people with no visual confirmation of the killer but just some blood samples of the killer, DNA evidence testing might still not be used in a case like this despite the crime happening in a relatively small community.
Also, since DNA evidence testing relies on the gene and there is a lot of research going on at the moment on genes (including gene mapping and locus system) which can assist to lower the number of suspects by predicting the origins of suspects. It should be noted that reducing the number of suspects reduces the amount that will be spent on DNA analysis of the suspects (since there are fewer suspects).
