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Table 3 Scoring scheme for strength of argument

From: Promoting productive argumentation through students' questions

Component of argument Description Score
Determining the cause of death: Support intravenous injection
Evidence 1 Livor Mortis showed dark purplish red distribution found on back of shoulders, back of arms, back of waist and back of legs 1
Warrant 1 Victim was lying on her back when she died – those area that does not comes in contact with her bed showed no discolouration
Backing 1 Blood stopped circulating when the heart stopped beating. Blood cells settled (due to gravity) to the lowest areas in the body and accumulates in areas not in contact with any surface since the blood capillaries were not compressed.
Evidence 2 -Vial containing synthetic hormones (estrogen and anti-androgen) -Fresh jabs and healing wounds -Blood stain on needle Injected left and right radial vein showing fresh and old injection marks 1
Warrant 2 Hormones being injected in the deceased body as needed hormone to remain woman
Backing 2 Victim has XY chromosomes indicating that victim is a male by birth. Estrogen is a female hormone. Victim has intravenous injection for hormone therapy on regular basis
Evidence 3 Blockage in coronary artery leading to muscle death 1
Warrant 3 An air bubble/ air embolism may have blocked the coronary artery leading to muscle death
Backing 3 -A correct description of how air embolism can lead to restriction of blood flow to coronary arteries in atrial septic defective individual (this should include the blood vessels involved). -Limited supply of oxygenated blood to cardiac muscles. With the lack of oxygen and nutrients, cardiac muscles eventually die.
Determining the cause of death: Refute drowning
Evidence 4 -Presence of red fluid, mixture of river water (similar to those in crime scene 1) and haemoglobin can be found in the lungs -Blood extracted from pulmonary capillaries showed lysis of red blood cells 1
Warrant 4 Pressure in the victim’s lungs was lower than her surrounding Osmosis occurs since river water had a higher water potential than the red blood cells.
Backing 4 River water entered lungs due to pressure differences, water molecules moved from alveoli to pulmonary capillaries. Water molecules entered into red blood cells and lysed red blood cells, releasing haemoglobin which diffused across into the alveoli spaces.
Evidence 5 High level of potassium ions in blood 1
Warrant 5 Lysis of red blood cells and cardiac muscle damage due to warrant 3 and backing 3 releases potassium ions.
Backing 5 Red blood cells and cardiac muscle contains potassium ions
Qualifier
Claim So, the cause of death was cardiac arrest due to air embolism as a result of intravenous injection